Hydraulically settable containers and other articles for storing, dispensing, and packaging food and beverages and methods for their manufacture

ABSTRACT

Containers incorporating a hydraulically settable structural matrix including a hydraulically settable binder such as cement for use in the storing, dispensing, and/or packaging of food and beverage products are disclosed. The disposable and nondisposable food and beverage articles of manufacture have high tensile, compressive, and flexural strengths, and are lightweight, insulative (if desired), inexpensive, and more environmentally compatible than those currently used. These disposable containers and cups are particularly useful for dispensing hot and cold food and beverages in the fast food restaurant environment. The structural matrix of the food and beverage containers includes a hydraulic cement paste (formed from the reaction of water with, e.g., a portland-type cement) preferably in combination with a theology-modifying plasticizer, such as methylhydroxyethylcellulose, various aggregate materials and fibrous materials which provide desired properties at a cost which is economical.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to containers and other articles ofmanufacture for use in storing, dispensing, and packaging food andbeverage products. More particularly, the present invention is directedto both disposable and nondisposable food and beverage containers andother articles manufactured from hydraulically settable materials thatcan be lightweight, insulative, inexpensive, and more environmentallyneutral than those currently used in the storing, dispensing (e.g.,serving or portioning), and packaging of food and beverage products.Disposable containers and cups within the scope of the present inventionare particularly useful for dispensing hot and cold food and beveragesin the fast food restaurant environment.

2. Related Applications

This application is a continuation-in-part of copending application Ser.No. 07/929,898 entitled "Cementitious Food and Beverage Storage,Dispensing, and Packaging Containers and the Methods of ManufacturingSame," filed Aug. 11, 1992, in the names of Per Just Andersen, Ph.D.,and Simon K. Hodson (now abandoned). This application is also acontinuation-in-part of copending application Ser. No. 08/019,151entitled "Cementitious Materials for Use in Packaging Containers andTheir Methods of Manufacture," filed Feb. 17, 1993, in the names of PerJust Andersen, Ph.D., and Simon K. Hodson, pending. For purposes ofdisclosure, both of these applications are incorporated herein byspecific reference.

3. The Relevant Technology

A. Food and Beverage Containers

Today, the world enjoys food and beverages products which are safer thanever before. Advanced processing and packaging techniques allow foods totravel safely for long distances from their point of origin. Even withlengthy and time-consuming distribution networks, today's food productsarrive in a wholesome condition. Packaging protects food fromenvironmental influences and distribution damage, particularly chemicaland physical influence and damage. Packaging also provides a medium forthe dissemination of information to the consumer: for example,nutritional information, cooking instructions, ingredients, productweight, advertising, brand identification, and pricing.

Packaging helps protect food products from gases, moisture, light,microorganisms, vermin, physical shock, crushing forces, vibration,leaking, or spilling. In addition, goods may be dispensed using specificpackaging aids, such as disposable cups, plates, or boxes (such as the"clam shell" frequently used in the fast food industry for burgers,sandwiches, and salads).

Typically, such disposable containers and cups are made from paper(including cardboard), plastic (particularly polystyrene), glass, andmetal materials. Paper and metal products are particularly useful withcold beverages and food products. Each year over one hundred billionaluminum cans, billions of glass bottles, and thousands of tons of paperand plastic are used in storing and dispensing soft drinks, juices, andbeer.

Hot items (such as fast food and many drinks) require a container thatis insulated to slow the loss of heat, both to keep the item hot and toprotect the consumer from being burned. The container of choice inrecent years has typically been made from polystyrene. Although paper orplastic coated containment products can be equipped with specialhandles, polystyrene containers have remained the superior disposablecontainer of choice when insulation is required, because insulationcapabilities, cost, and stability.

In spite of the more recent attention that has given to reduce the useof paper and plastic materials, they continue to be used because ofstrength properties and mass producibility. Moreover, for any given usefor which they are designed, such materials are relatively inexpensive,lightweight, easy to mold, strong, durable, and resistant degradationduring use.

B. The Impact of Paper, Plastic, Glass and Metal

Recently there has been a debate as to which of these materials (e.g.,paper, polystyrene, glass, or metal cans) is most damaging to theenvironment. Consciousness-raising organizations have convinced manypeople to substitute one material for another in order to be moreenvironmentally "correct." The debate often misses the point that eachof these materials has its own unique environmental weaknesses. Onematerial may appear superior to another when viewed in light of aparticular environmental problem, while ignoring different, oftenlarger, problems associated with the supposedly preferred material. Infact, paper, cardboard, plastic, polystyrene, glass, and metal materialseach has own unique environmental weaknesses.

Polystyrene products have more recently attracted the ire ofenvironmental groups, particularly containers and other packagingmaterials. While polystyrene itself is a relatively inert substance, itsmanufacture involves the use of a variety of hazardous chemicals andstarting materials. Unpolymerized styrene is very reactive and thereforepresents a health problem to those who must handle it. Because styreneis manufactured from benzene (a known mutagen and probably acarcinogen), residual quantities of benzene can be found in styrene.

More potentially damaging has been the use of chlorofluorocarbons (or"CFCs") in the manufacture of "blown" or "expanded" polystyreneproducts. This is because CFCs have been linked to the destruction ofthe ozone layer. In the manufacture of foams, including blownpolystyrene, CFCs (which are highly volatile liquids) have been used to"expand" "blow" the polystyrene into a foamed material, which is thenmolded into the form of cups, plates, trays, boxes, "clamshell"containers, spacers, or packaging materials. Even the substitution ofless "environmentally damaging" blowing agents (e.g., HCFC, CO₂, andpentanes) are still significantly harmful and their elimination would bebeneficial.

As a result, there has been widespread pressure for companies to stopusing polystyrene products in favor of more environmentally safematerials. Some environmental groups have favored a temporary return tothe use of natural produces such as paper or wood, which are believed tobe biodegradable. Nevertheless, other environmental groups have takenthe opposite view in order to minimize cutting trees and depleting theforests.

Although paper products are ostensibly biodegradable and have not beenlinked to the destruction of the ozone layer, recent studies have shownthat the manufacture of paper probably more strongly impacts theenvironment than does the manufacture of polystyrene. In fact, the woodpulp and paper industry has been identified as one of the five toppolluters in the United States. For instance, products made from paperrequire ten times as much steam, fourteen to twenty times theelectricity, and twice as much cooling water compared to an equivalentpolystyrene product. Various studies have shown that the effluent frompaper manufacturing contains ten to one hundred times the amount ofcontaminants produced in the manufacture of polystyrene foam.

In addition, a by-product of paper manufacturing is that the environmentis impacted by dioxin, a harmful toxin. Dioxin, or more accurately,2,3,7,8-tetrachlorodibenzo[b,e][1,4]dioxin, is a highly toxic, terageniccontaminant, and is extremely dangerous even in very low quantities.Toxic effects of dioxin in animals and humans include anorexia, severeweight loss, hepatoxicity, hematoporphyria, vascular lesions, chloracne,gastric ulcers, porphyrinuria, porphyria, cutanea tarda, and prematuredeath. Most experts in the field believe that dioxin is a carcinogen.

The highest level of dioxin allowed in the discharge waters from papermills is about 0.5 part per trillion. However, fish found downstreamfrom paper pulp mills can contain nearly 200 parts per trillion ofdioxin, with levels of 50 parts per trillion being not uncommon.

The manufacturing processes of metal cans (particularly those made ofaluminum and tin), glass bottles, and ceramic containers for food andbeverages utilize high amounts of energy because of the necessity tomelt and then separately work and shape the raw metal into anintermediate or final product. These high energy and processingrequirements not only utilize valuable energy resources, but they alsoresult in significant air, water, and heat pollution to the environment.

With glass and ceramic materials, in addition to the high processingcosts, the final food and beverage product brittle. Further, while glasscan be recyled, that portion which ends up in landfills is essentiallynonbiodegradable. (For purposes of convenience, since the many of theproblems of metal materials, when compared to the products of thepresent invention, are the same as with glass and ceramic materials,reference hereinafter will generally be made to metal prior artmaterials and problems. However, it will be appreciated that many, ifnot most, of the same comments are applicable to food and beveragecontainers made from glass or ceramic materials.)

Some of these pollution problems are being addressed; however, theresult is the use of more energy, as well as the significant addition tothe capital requriements for the manufacturing facilities. Further,while significant efforts have been expended in recycling programs, onlya portion of the raw material needs come from recycling--most of the rawmaterial set comes from nonrenewable resources.

A huge variety of objects such as containers, packing materials, mats,disposable utensils, cans, and decorative items are presentlymass-produced from paper, plastic, and metal. Unfortunately, the vastmajority of paper and polystyrene (and even metal) items eventually windup within our ever diminishing landfills, or worse, are scattered on theground or dumped into bodies of water as litter. Because plastic andmetals are essentially nonbiodegradable, they persist within the landand water as unsightly, value diminishing, and (in some cases) toxicforeign materials.

Even paper or cardboard, believed by many to be biodegradable, canpersist for years, even decades, within landfills where they areshielded from air, light, and water, all of which are required fornormal biodegradation activities. There are reports of telephone books,and newspapers having been lifted from garbage dumps that had beenburied for decades. This longevity of paper is further complicated sinceit is common to treat, coat, or impregnate paper with various protectivematerials which further slow or prevent degradation.

Another problem with paper, cardboard, polystyrene, and plastic is thateach of these requires relatively expensive organic starting materials,some of which are nonrenewable, such as the use of petroleum in themanufacture of polystyrene and plastic. Although trees used in makingpaper and cardboard are renewable in the strict sense of the word, theirlarge land requriements and rapid depletion in certain areas of theworld undermines this notion. Hence, the use of huge amounts ofessentially nonrenewable starting materials in making disposablecontainers cannot be sustained and is not wise from a long termperspective. Furthermore, the processes used to make the packaging stockraw materials (such as paper pulp, styrene, or metal sheets) are veryenergy intensive, cause major amounts of water and air pollution, andrequire significant capital requirements.

In light of the foregoing, the debate should not be directed to which ofthese materials is more or less harmful to the environment, but rathertoward asking: Can we discover or develop an alternative material whichwill solve most, if not all, of the various environmental problemsassociated with each of these presently used materials.

3. Traditional Hydraulically Settable Materials

On the other hand, for millennia, man has made great use ofnondepletable inorganic materials such as clay or stone. Similarly,hydraulically settable materials such as those that contain hydrauliccement or gypsum (hereafter "hydraulically settable," "hydraulic," or"cementitious" compositions, materials, or mixtures) have been used forthousands of years to create useful, generally large, bulky structuresthat are durable, strong, and relatively inexpensive. For example,cement is a hydraulically settable binder derived from clay andlimestone, and it is essentially nondepletable.

Those materials containing a hydraulic cement are generally formed bymixing hydraulic cement with water and usually some type of aggregate toform a cementitious mixture, which hardens into concrete. Ideally, afreshly mixed cementitious mixture is fairly nonviscous, semi-fluid, andcapable of being mixed and formed by hand. Because of fluid nature,concrete is generally shaped by being poured into a mold, worked toeliminate large air pockets, and allowed to harden. If the surface ofthe concrete structure is to be exposed, such as on a concrete sidewalk,additional efforts are made to finish the surface to make it morefunctional and to give it the desired surface characteristics.

Due to the high level of fluidity required for typical cementitiousmixtures to have adequate workability, the uses of concrete and otherhydraulically settable mixtures have been limited mainly to simpleshapes which are generally large, heavy, and bulky, and which requiremechanical forces to retain their shape for an extended period of timeuntil sufficient hardening of the material has occurred. Another aspectof the limitations of traditional cementitious mixtures or slurries isthat they have little or no form stability and are molded into the finalform by pouring the mixture into a space having externally supportedboundaries or walls.

It is precisely because of this lack of moldability (which may be theresult of poor workability and/or poor form stability), coupled with thelow tensile strength per unit weight, that cementitious materials havetraditionally been useful only for applications where size and weightare not limiting factors and where the forces or loads exerted on theconcrete are generally limited to compressive forces or loads, as in,e.g., roads, foundations, sidewalks, and walls.

Moreover, cementitious materials have historically been brittle, rigid,unable to be folded or bent, and of low elasticity, deflection andflexural strength. The brittle nature and lack of tensile strength(about 1-4 MPa) in concrete is ubiquitously illustrated by the fact thatconcrete readily cracks or fractures upon the slightest amount ofshrinkage or bending, unlike other materials such as metal, paper,plastic, or ceramic. Consequently, typical cementitious materials havenot been suitable for making small, lightweight objects, such ascontainers or thin sheets, which are better if made from materials withmuch higher tensile and flexural strengths per unit weight compared totypical cementitious materials.

More recently, higher strength cementitious materials have beendeveloped which might be capable of being formed into smaller, denserobjects. One such material is known as "Macro-defect Free" or "MDF"concrete, such as is disclosed in U.S. Pat. No. 4,410,366 to Birchall etal. See also, S. J. Weiss, E. M. Gartner & S. W. Tresouthick, "HighTensile Cement Pastes as a Low Energy Substitute for Metals, Plastics;Ceramics, and Wood," U.S. Department of Energy CTL Project CR7851-4330(Final Report, November 1984).

However, such high strength cementitious materials have beenprohibitively expensive and would be unsuitable for making inexpensivecontainers where much cheaper materials better suited for such uses(e.g., paper and plastic) are readily available. Another drawback isthat MDF concrete cannot be used to mass produce small lightweightobjects due to the high amount of time and effort involved in formingand hardening the material and the fact that it is highly water soluble.Therefore, MDF concrete has been limited to expensive objects of simpleshape.

Another problem with traditional, and even more recently developed highstrength concretes, has been the lengthy curing times almost universallyrequired for most concretes. Typical concrete products formed from aflowable mixture require a hardening period of 10-24 hours before theconcrete is mechanically self-supporting, and upwards of a month beforethe concrete reaches a substantial amount of its maximum strength.Extreme care has had to be used to avoid moving the cementitiousarticles until they have obtained sufficient strength to be demolded.Movement or demolding prior to this time has usually resulted in cracksand flaws in the cementitious structural matrix. Once self-supporting,the object could be demolded, although it has not typically attained themajority of its ultimate strength until days or even weeks later.

Since the molds used in forming cementitious objects are generallyreused in the production of concrete products and a substantial periodof time is required for even minimal curing of the concrete, it has beendifficult to economically and commercially mass produce cementitiousobjects. Although zero slump concrete has been used to produce large,bulky objects (such as molded slabs, large pipes, or bricks which areimmediately self-supporting) on an economically commercial scale, suchproduction is only useful in producing objects at a rate of a fewthousand per day. Such compositions and methods cannot be used to massproduce small, thin-walled objects at a rate of thousands per hour.

Demolding a cementitious object can create further problems. As concretecures, it tends to bond to the forms unless expensive releasing agentsare used. It is often necessary to wedge the forms loose to remove them.Such wedging, if not done properly and carefully each time, oftenresults in cracking or breakage around the edges of the structure. Thisproblem further limits the ability to make thin-walled cementitiousarticles or shapes other than flat slabs, particularly in any type of acommercial mass production.

If the bond between the outer wall of the molded cementitious articleand the mold is greater than the internal cohesive or tensile strengthsof the molded article, removal of the mold will likely break therelatively weak walls or other structural features of the moldedarticle. Hence, traditional cementitious objects must be large involume, as well as extraordinarily simple in shape, in order to avoidbreakage during demolding (unless expensive releasing agents and otherprecautions are used).

Typical processing techniques of concrete also require that it beproperly consolidated after it is placed in order to ensure that novoids exist between the forms or in the structural matrix. This isusually accomplished through various methods of vibration or poking. Theproblem with consolidating, however, is that the more extensive theconsolidation of the concrete after it has been placed, the greater thesegregation or bleeding of the concrete.

"Bleeding" is the migration of water to the top surface of freshlyplaced concrete caused by the settling of the aggregate. Excessivebleeding increases the water-to-cement ratio near the top surface of theconcrete slab, which correspondingly weakens and reduces the durabilityof the surface of the slab. The overworking of concrete during thefinishing process not only brings an excess of water to the surface, butalso some fine material, thereby resulting in inhomogeneity ornonuniformity which manifest themselves as subsequent surface defects.

For each of the foregoing reasons, as well as numerous others whichcannot be listed here, cementitious materials have not generally hadapplication outside of the formation of large, slab-like objects, suchas in buildings, foundations, walk-ways, or highways, or as mortar toadhere bricks or cured concrete blocks. It is completelycounterintuitive, as well as contrary to human experience, to evenimagine the manufacture of small lightweight objects (such as containerscomparable to the lightweight materials made from paper, plastic, ormetal) from cementitious materials within the scope of the presentinvention.

Due to the more recent of the tremendous environmental impacts of usingpaper, cardboard, plastic, polystyrene, and metals for a variety ofsingle-use, mainly disposable items such as containers (not to mentionthe ever mounting political pressures), there has been an acute need(long since recognized by those skilled in the art) to findenvironmentally sound substitute materials, such as cementitiousmaterials, for these disposable items.

In spite of such pressures and long-felt need, the technology simply hasnot existed for the economic and feasible production of cementitiousmaterials which could be substituted for paper, cardboard, plastic,polystyrene, or metal products such as containers. However, becausecementitious materials essentially comprise such environmentally neutralcomponents such as rock, sand, clay, and water, they would be ideallysuited, from an ecological standpoint, to replace paper, cardboard,plastic, or polystyrene materials as the material of choice for suchapplications.

Such materials are not only made from nondepletable components, they donot impact the environment nearly as much as do paper, cardboard,plastic, and polystyrene. Another advantage of cementitious and otherinorganic materials is that they are far less expensive than paper,cardboard, plastic, polystyrene, or metals.

While paper, cardboard, plastic, polystyrene, and metal products mightbe comparably priced to each other, they are far more expensive thantypical cementitious materials. Because no rational business wouldignore the economic benefit which would necessarily accrue from thesubstitution of radically cheaper cementitious materials for paper,cardboard, plastic, polystyrene, or metals, the failure to do so canonly be explained by a marked absence of available technology to makesuch a substitution.

In light of the foregoing, what is needed are new materials other thanpaper, cardboard, plastic, or polystyrene which can be used in themanufacture of containers used in storing, dispensing, and packagingfood or beverages. Such materials would represent a significantadvancement in the art if they could be made without relying so heavilyon the use of trees, petroleum, or other essentially nonrenewable orslowly renewing resources as the source of the primary startingmaterial.

It would yet be an advancement in the art if such materials were moreenvironmentally neutral, both in their manufacture and in theirdisposal. More particularly, would be a tremendous advancement in theart if the manufacture of food and beverage containers did not result inthe release of dioxin, CFCs or other dangerous chemicals into theenvironment, as does the use of presently used materials. Similarly, itwould be an advancement if such containers were essentially made ofcomponents found naturally within the earth into which they mayeventually be discarded.

It would be a significant advancement if such materials could be made tocontain a high percentage of air voids so as to provide the insulationproperties of containers made from polystyrene. It would yet be asignificant advancement in the art if such materials could also be madeto have properties of strength and aesthetics similar to those of paper,plastic, or thin metal.

It would be a significant improvement if such new materials could bemade to have each of the properties found in existing materials used tomake all of the various food and beverage containers found in themarketplace. This improvement would be even more important if suchmaterials could be made to possess yet other properties not found in anyof the existing materials (such as long shelf life, noncorrosive, andfire and heat resistant), which could exploited to manufacture new foodand beverage containers which have not hitherto been possible.

From a practical point of view, it would be a significant improvement inthe art if such materials used in the manufacture of food and beveragecontainers could be produced at a cost that was comparable to, and evenless expensive than, existing containers.

From a manufacturing perspective, it would be a significant advancementin the art if such materials could rapidly obtain form stability,maintain their shape without external support, and be handled in amanner similar to other materials presently used to manufacture food andbeverage containers.

Such materials used to manufacture food and beverage containers aredisclosed and claimed herein.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

The present invention relates to novel compositions and methods for themanufacture of food and beverage containers made from hydraulic settablematerials. It has been found that lightweight, strong, andenvironmentally compatible (and if desired, flexible or insulative) foodand beverage containers can be readily and inexpensively mass producedfrom hydraulically settable materials, including cement and gypsum,through innovative processes developed through materials science andmicrostructural engineering approaches. Disposable containers, cups, andother article of manufacture within the scope of the present inventionare particularly useful for dispensing hot and cold food and beveragesin the fast food restaurant environment.

The materials science and microstructural engineering approaches of thepresent invention build into the microstructure of the hydraulicallysettable compositions of the present invention the desired physicalcharacteristics and properties, while at the same time remainingcognizant of costs and other complications involved in the large scalemanufacturing systems. In doing so, many of the problems have beenovercome which have historically relegated the use of most hydraulicallysettable matterials to bulky, massive structural objects.

As discussed in greater detail hereinafter, the materials science andmicrostructural engineering approaches, instead of the traditionaltrial-and-error, mix-and-test approach, specifically allow for thedesign of hydraulically settable materials with the properties of hightensile and flexural strength, high insulation, low weight, low cost,and low environmental impact desired for disposable food and beveragecontainers. Control of the design of the hydraulically settablecompositions on the microstructural level has come, in part, from thediscovery that during formation of an object either (a) the rheology ofthe composition should be chemically modified to give moldability andrapid form stability, or (b) the water-to-cement ratio of thecomposition should be reduced by processing or by adding energy.

The result is the ability to mass produce on a commercially viable scalea wide variety of food and beverage containers and articles (includingmany which are disposable) from hydraulically settable materials at acost that is usually competitive with, and in most cases even superiorto, the cost involving using other materials. Moreover, because thehydraulically settable materials of the present invention compriseenvironmentally neutral components, the manufacture of food and beveragecontainers therefrom impacts the environment to a much lesser extentthan does the manufacture of containers from these other materials. Thehydraulically settable materials of the present invention preferably donot require the use of high concentrations of wood pulp or petroleumproducts as does the manufacture of food and beverage containers frompaper, cardboard, plastic, polystyrene, or metals.

The major components within the hydraulically settable materials of thepresent invention include mainly inorganic materials, such as ahydraulic binder (like cement or gypsum), aggregates (like perlite,sand, glass, silica, vermiculite, clay, mica, and even waste concreteproducts), and sufficient water to hydrate, or react with, the hydraulicbinder.

Although certain embodiments may also include organic components, suchas cellulose-based fibers and/or rheology-modifying agents, theserepresent a small fraction of the overall mass of the hydraulicallysettable materials used to manufacture food and beverage containers.Together, the organic components will make up usually less than about30% by volume of the unhardened hydraulically settable mixture;preferably, this fraction will be less than about 15% by volume.

However, due to the versatility of the hydraulically settable mixturesused in the manufacture of food and beverage containers, a wide range offibers, both organic and inorganic, can be used. Any abundant fiber, notjust wood fiber, but preferably those that can be planted and harvestedin an agribusiness setting, works well within the invention. The use ofsuch fibrous materials would have the additional beneficial effect ofpreserving our dwindling forests.

In any event, natural fibers from, e.g., wood, flax, abaca, hemp,cotton, and bagasse are preferred. Because they are held together with ahydraulic binder, they do not require the intense processing used tomake most paper or cardboard products. Such processes are necessary inthe paper industry in order to release the lignin within the wood pulpand to fray the fibers in order to achieve a web effect between thefibers in order to bind the fibers together. No such intense processingis necessary in the present invention, which to a major extent preservesthe strength of the fibers and allows them to be included in far lesseramounts while still deriving a high level of strength therefrom.

Hence, the advantages of fibers can be incorporated into a hydraulicbinder, with the addition of smaller concentration and without theextensive processing as in paper. Further, contaminated water is not asignificant byprodcut in the processing of the present invention, as isthe case in paper production.

Unlike the manufacture of plastic or polystyrene, the hydraulicallysettable materials of the present invention utilize little or nopetroleum-based products or derivatives as starting materials. Thus,although some amount of fossil fuel is necessary to generate the energyused in manufacturing the hydraulically settable containers, only afraction of the petroleum used in the manufacture of polystyrene orplastic products will be consumed overall. In addition, the energyrequirements of the present invention are much less than the energyrequirements of paper manufacturing; similarly, the initial capitalinvestments can be less with the present invention.

Finally, another advantage of the hydraulically settable containers ofthe present invention is that their disposal impacts the environmentless than paper and cardboard products, and much less than plastic orpolystyrene products. The hydraulically settable materials of thepresent invention can be readily recycled. Nevertheless, even if notrecycled, the hydraulically settable containers of the present inventioncan be discarded and reduced to a fine granular powder which has acomposition complementary to the components of the earth into which itwill be placed.

This disintegration process is not dependent on biodegradation forcesbut will occur as the result of various forces which may be present,such as moisture and/or pressure. For example, the rheology-modifyingagent will dissolve over time through exposure to water, therebycreating voids within the matrix of the material. These voids make thematerial soft and easier to crush. In addition, both therheology-modifying agent and the cellulose fibers are biodegradable(i.e., subject to breakdown by microorganisms, heat, light, and water).

If the hydraulically settable waste materials are discarded into alandfill, they will crumble into a fine granular powder under the weightof the other garbage present, thereby increasing the specific surfacearea available for further biodegradation and erosion. If discarded onthe ground, the forces of water and wind, and even fortuitouscompressive forces, such as from cars running over them or peoplestepping on them, will cause the hydraulically settable waste materialsto be reduced to a substantially inorganic, more innocuous granularpowder in a short period of time relative to the time it usually takesfor the typical disposable paper or polystyrene foam cup to decomposeunder the same circumstances.

A plastic or metal cup or can thrown into a lake or stream will last fordecades, perhaps even centuries, while a hydraulically settablecontainer will dissolve in a short period of time into essentially adirt-like sand or mud, the time of dissolution being dependent largelyon the mix design of the hydraulically settable mixture used tomanufacture the container.

The preferred structural matrix of the food and beverage containersmanufactured according to the present invention is formed from thereaction products of a cementitious or other hydraulically settablemixture. A hydraulically settable mixture will at a minimum contain ahydraulic binder, such as hydraulic cement or gypsum hemihydrate, andwater.

In order to design the desired specific functional properties into thehydraulically settable mixture and/or the hardened structural matrix fora specific container, a variety of other additives can be includedwithin the hydraulic mixture, such as rheology-modifying agents,dispersants, one or more aggregate materials, fibers, air entrainingagents, blowing agents, or reactive metals. The identity and quantity ofany additive will depend on the desired properties or performancecriteria of both the hydraulically settable mixture as well as the finalhardened container made therefrom.

Rheology-modifying agents can be added to increase the cohesivestrength, "plastic-like" behavior, and the ability of the mixture toretain its shape when molded or extruded. They act as thickeners andincrease the yield stress of the hydraulically settable mixture, whichis the amount of force necessary to deform the mixture. This createshigh "green strength" in the molded or extruded product. Suitablerheology-modifying agents include a variety of cellulose-, starch-, andprotein-based materials (which are generally highly polar), all of whichassist in bridging the individual particles together.

Dispersants, on the other hand, act to decrease the viscosity and theyield stress of the mixture by dispersing the individual hydraulicbinder particles. This allows for the use of less water whilemaintaining adequate levels of workability. Suitable dispersants includeany material which can be adsorbed onto the surface of the hydraulicbinder particles and which act to disperse the particles, usually bycreating a charged area on the particle surface or in the near colloiddouble layer.

In the case where both a rheology-modifying agent and a dispersant areused, it will usually be advantageous to add the dispersant first andthe rheology-modifying agent second in order to obtain the beneficialeffects of each. Otherwise, if the rheology-modifying agent is firstadsorbed by the binder particles, it may create a protective colloidlayer, which will prevent the dispersant from being adsorbed by theparticles and imparting its beneficial effect to the hydraulicallysettable mixture.

It may be preferable to include one or more aggregate materials withinthe hydraulically settable mixture in order to add bulk and decrease thecost of the mixture. Aggregates often impart significant strengthproperties and improve workability. An example of one such aggregate isordinary sand or clay, which is completely environmentally safe,extremely inexpensive, and essentially inexhaustible.

In other cases, lightweight aggregates can be added to yield a lighter,and often more insulating, final product. Examples of lightweightaggregates are perlite, vermiculite, hollow glass spheres, aerogel,xerogel, pumice, and other lightweight, rocklike materials. Theseaggregates are likewise environmentally neutral and relativelyinexpensive.

Fibers may be added to the hydraulically settable mixture in order toincrease the compressive, tensile, flexural, and cohesive strengths ofthe wet material as well as the hardened container made therefrom. Inthe case where a food or beverage container is made from a hardenedsheet, the inclusion of fibers will allow the hydraulically settablesheet to be rolled up, scored, or folded into the desired shape of afood or beverage container. Fiber should preferably have high tear andburst strengths (i.e., high tensile strength), examples of which includeabaca, southern pine, flax, bagasse (sugar cane fiber), cotton, andhemp. Fibers with a high aspect ratio work best in imparting strengthand toughness to the hydraulically settable material.

One significant aspect of the present invention is that the food andbeverage containers can be economically and mass produciblymanufactured. The food and beverage products disclosed herein are notintended to be handmade at the rate of a few at a time, but are intendedto be made at the rate of hundreds, thousands, or tens of thousands perhour. The creation of new materials that can be rapidly processed insuch a manner (that is, similar to paper, plastic, or metals) comes fromutilization of one of the following approaches during the manufacturingprocess: (a) chemically modifying the hydraulically settable mixture(such as by the addition of a rheology-modifying agent) in order to givethe mixture workability and then rapid form stability, or (b) reducingthe water-to-cement ratio during the formation process (such as by theaddition of energy in the form of heat or pressure). The application ofthese principles will become readily apparent from the following methodsof manufacture.

Preferred methods of manufacturing hydraulically settable containerswithin the scope of the present invention include the steps of: (1)mixing a hydraulic binder and water in order to form a hydraulic paste,often in a high shear mixer; (2) adding other desired materials such asa rheology-modifying agent, dispersant, aggregates, and fibers to createa hydraulically settable mixture having the desired rheological as wellas ultimate strength, weight, insulative, and low cost properties; and(3) forming an appropriate food or beverage container from thehydraulically settable mixture. The forming step (including molding thehydraulically settable mixture) may be carried out using a variety ofmethods; the three currently preferred methods include: (a) directlymolding the article from a quantity of the hydraulic mixture, (b)molding or stamping the article from a moistened sheet of the mixture,and (c) forming the article by rolling, bending or folding asubstantially dry sheet molded from the material. These methods areherein referred to as "direct molding," "wet sheet molding," and "drysheet molding," respectively.

According to the presently preferred "direct molding" manufacturingmethod, the hydraulically settable mixture (prepared as described above)having the desired properties is positioned between a male die of adesired shape and a female die having a shape substantiallycomplementary to that of the male die. The mixture is typicallypositioned by partially mating the dies and then injecting, such as byan auger-type (either single or double) or piston-type extruder, themixture between the dies. Alternatively, a quantity of the mixture canbe placed on a first die such that as the first die is mated with asecond die, the mixture is positioned between the dies.

Next, the mixture is pressed between the dies so as to mold the mixtureinto the desired shape for the container. The types of dies that can beused include solid, split, and progressive dies. The type of dieselected depends on the size, shape, and complexity of the containerbeing manufactured.

To economically produce the containers and articles, the fashionedcontainers must quickly obtain form stability. In one embodiment, thedies are each heated to a predetermined temperature so as to rapidly drythe surface of the container, thereby creating a form-stable container.Heating the dies also functions to form a steam barrier that minimizesthe adhering of the container to the dies. Additional methods, such ascooling the dies or adding a nonhydrating liquid that rapidlyevaporates, can also be used to quickly impart form stability to thecontainers. Still other methods used impart form stability include theaddition of gypsum hemihydrate, carbonate sources, accelerators, methylcellulose, starch, and fibers to the mixture or limiting line amount ofwater in the mixture.

Once the containers obtain sufficient form stability, they can beremoved from the dies. Removal from the dies typically accomplished byairveying, or sucking the containers off the mold. Alternatively, atemplate can be used to lift the containers off the mold.

Finally, the containers are passed through a drying apparatus to driveoff additional amounts of water within container, thereby increasing thestrength and improving the form stability of the container. The heatimparted by the drying apparatus also increases the rate of hydration ofthe hydraulic cement and reduces the time in which the cementitiousmatrix hardens. Once the container has obtained sufficient strength, thecontainer can be packaged and shipped.

In the currently preferred embodiment of the "wet sheet molding" processfor manufacturing the food and beverage articles, the hydraulicallysettable mixture having the desired characteristics (prepared accordingto the procedure described above) is extruded through a die, forexample, auger- or piston-type extruder, into relatively thin sheets ofa predetermined thickness. In one embodiment, a vacuum is attached tothe auger to remove excess air from the mixture.

The extruded sheets are then "calendered" by passing them between a setof reduction rollers to form sheets with a more uniform thickness and asmoother surface. The rollers can be heated to create a steam barrierthat minimizes adherence between the rollers and hydraulically settablemixture. Heating the rollers also has the effect of driving off aportion of the water within the sheets. Likewise, the rollers can alsobe cooled to prevent sticking of the mixture. In some cases, it may bepreferable to pass the sheets through a series of sets of rollers havingprogressively smaller distances between the sets of rollers to obtain acalendered sheet having a progressively thinner thickness.

In addition, by using a pair of rollers having different orientations inthe "Z" direction (or normal to the surface of the sheet), such as byusing a flat roller paired with a conical roller, a percentage of thefibers can be oriented in the "X" (or width-wise) direction. In thisway, a sheet having bidirectionally oriented fibers can be manufactured.This is thought to occur because the conical roller can widen the sheetin the "X" direction. Sheets having bidirectionally aligned fibersproduce containers having a more uniform strength.

A portion of the sheet is then fashioned into a desired shape for acontainer or article. This is preferably accomplished by pressing thesheet between a male die of a desired shape and a female die having asubstantially complementary configuration of the male die shape.Alternative types of dies that can be used include split dies andprogressive dies. The containers can also be formed by applying one ofmany vacuum forming techniques to the hydraulically settable sheets.

As with the direct molding process, the containers are then passedthrough a drying apparatus to drive off additional amounts of waterwithin the container to increase it strength, improve the form stabilityof the container, increase the rate of hydration of the hydrauliccement, and reduce the time in which the cementitious matrix ultimatelyhardens. In fact, each of the techniques used to obtain rapid formstability in the direct molding process can also be used in the wetsheet molding process. Finally, the containers are cut from theremaining sheet.

The presently preferred "dry sheet molding" method of manufacturingcontainers from hydraulically settable sheets within the scope of thepresent invention includes the stems of: (1) placing the hydraulicallysettable mixture (prepared as described above) into an extruder, such asan auger or piston extruder, in a manner substantially the same as in"wet sheet molding" process; (2) while providing a means deairing thehydraulic mixture, extruding the mixture through an appropriate die topreferably form a flat sheet of a desired thickness or a pipe that canbe unfolded into a sheet; (3) as in the "wet sheet molding" process,reducing the thickness of the sheet by passing it between at least onepair of rollers; and (4) drying the sheet to create a substantiallyhardened structural matrix.

In addition, the sheet can be optionally compacted while still in aslightly moistened condition in order to eliminate unwanted voids withinthe structural matrix, increase the fiber adhesion, reduce porosity,and/or increase surface smoothness. This is carried out by passing thesheet between one or more separate sets of compaction rollers. Bycarefully controlling the water content, it will be possible to ensurethat the compaction rollers only compress and increase the density ofthe sheet without further elongating the sheet.

The compaction step improves the strength of the final hardened sheet bycreating a more uniform structural matrix while also leaving the sheetwith a smoother finish. The optional compaction step is generallypreferred in the case of thinner sheets, where strength per unit ofthickness should be maximized and where insulation ability is lessimportant. Compaction is generally unnecessary for thicker sheetsintended to have high insulation and/or low weight characteristics.

The sheet can also be optionally scored, score cut, or perforated whilein a slightly moistened or even in the dry condition in order to createa line within the structural matrix upon which the sheet can later behinged or bent. Optionally, the sheet could be passed through a set ofcorrugation rollers in order to produce a corrugated sheet and/orcardboard.

Before, during, or after any of the three foregoing molding processes,coatings may be applied to the surface of a substantially dried sheet orcontainer for a number of reasons, such as to make the container morewaterproof, more flexible, or to give it a glossier surface. Coatingsbased upon materials such as soybean and methocel, alone or incombination with polyethylene glycol, can be applied to the surface inorder to permanently soften the sheet or container or hinge within thecontainer.

Elastomers, plastic, or paper coatings can aid in preserving theintegrity of a fold or hinge (if used), whether or not the underlyinghardened structural matrix fractures upon bending at the hinge. It maybe also desirable to print or emboss the sheets or containers withindicia, logos, or other printed material.

Additional embodiments of the present invention include the addition ofair voids in order to add insulative properties (for both hot and coldfoods and beverages) to the cups and containers. These air voids arecreated by the incorporation of gas through various techniques into thecementitious mixture--one method being the mechanical incorporation ofair voids during the mixing process, and another being the incorporationof a gas which is chemically generated in situ within the cement paste.

The compositions of the present invention can be varied to yieldproducts of substantially different character. For example, verylightweight products (similar to that of polystyrene foam) with rigidwalls can be manufactured.For convenience, this first type of product issometimes herein referred to as a "foam-like" product.

Alternatively, products that have an appearance more like that of apottery or ceramic product can be made according to the presentinvention. However, the products of the present invention are muchlighter, typically having a bulk specific gravity less than about 1.5,whereas pottery or ceramic products typically have a bulk specificgravity of 2.0 or greater. This second type of product of the presentinvention is sometimes herein referred to as a "clay-like" product,because it is a zero-slump, form stable, hydraulically sortable materialthat still has excellent workability properties.

Both foam-like and clay-like materials may first be molded into a sheet(or a continuous roll), which is later stamped, pressed, scored, folded,or rolled into a desired container or other article of manufacture. Thisthird kind of product will be referred to as a "sheet-like" product,which will appear most like, and take the place of, paper or cardboardin many food and beverage containers.

A key feature of the microstructural engineering design of the presentinvention is the materials science optimization of each desired property(including minimization of cost). It is only because of the uniquemicrostructural engineering of the present invention that thecementitious mixtures can be molded into a thin-walled, complex,lightweight product such as a food and beverage container and stillmaintain its shape without external support during the green state untilhardening can be accomplished.

Indeed, the economic viability of mass producing food and beverage cupsfrom cementitious materials is only possible because the cementitiousmixture is self-supporting during the green state and will maintain itsmolded state throughout the curing process. In addition, thecompositions of the present invention importantly provide cementitiousmixtures that rapidly reach a sufficiently high tensile and compressivestrength so that the molded containers can be handled and manipulatedusing conventional means.

From the foregoing, it will be appreciated that an object of the presentinvention is the development of new hydraulically settable materialswhich can be used in place of paper, cardboard, plastic, or polystyrenein the manufacture of containers used in storing, dispensing, andpackaging food or beverages.

Further, another object and feature of the present invention is thedevelopment of materials which could be made without relying on trees,petroleum, or other essentially nonrenewable or slowly renewingresources to provide primary starting material.

Yet another object of the present invention is the development ofmaterials that are more environmentally neutral, both in theirmanufacture and in their disposal than paper, cardboard, plastic,polystyrene, and metal materials. A further object of the presentinvention is the development of products which require less energy andlower initial capital investments for manufacturing.

It is another object that the manufacture of such food and beveragecontainers does not result in the release of dioxin, CFCs or otherdangerous chemicals into the environment, as does the use of presentlyused materials. Similarly, it is an object that such containers areessentially made of components found naturally within the earth intowhich they may eventually be discarded.

It is another object and feature of certain embodiments of the presentinvention that such containers can be made to provide the insulationproperties of containers made from polystyrene foam.

It is yet another feature and object of the present invention to providematerials that can be made to have similar properties of strength andesthetics as paper, plastic, or metal materials.

Another object and feature of the present invention is to provide newmaterials that can be made to alternatively have each of the propertiesfound in existing materials used to make all of the various food andbeverage containers found in the marketplace. It is yet another objectand feature to provide new materials that can be made to possess yetother properties not found in any of the existing materials, which couldbe exploited to manufacture new food and beverage containers which havenot hitherto been possible.

Another object of the present invention is to provide new materials usedin the manufacture of food and beverage containers which can be producedat a cost that is comparable to, and even less expensive than, existingcontainers.

A further object and feature of the present invention is to providehydraulically settable materials which can rapidly obtain formstability, maintain their shape without external support, and be handledin a manner similar to other materials presently used to manufacturefood and beverage containers, such that cost-effective massproducibility is possible.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to novel hydraulically settablecompositions and methods used to manufacture containers and otherarticles of manufacture for use in the storing, dispensing, andpackaging of various food and beverage products. More particularly, thepresent invention is directed to disposable and nondisposablehydraulically settable food and beverage containers and cupsmanufactured which are lightweight, have a high tensile and flexuralstrength, have a low bulk density, are insulative if desired), can beproduced cost effectively, and which have a low environmental impactcompared to containers presently used to store, dispense, and packagefood and beverages, particularly in the fast food industry.

As discussed above, the cups and containers within the scope of thepresent invention can be made to have a variety of densities andphysical characteristics. "Foam-like," "clay-like," and "sheet-like"products can be manufactured, depending upon the concentrations andtypes of the materials used and the molding, casting, or extrusionprocess utilized.

I. General Discussion

A. Microstructural Engineering Design

As mentioned above, the food and beverage containers and articles of thepresent invention have been developed from the perspective ofmicrostructural engineering in order no build into the microstructure ofthe hydraulically settable material certain desired, predeterminedproperties, while at the same time remaining cognizant of costs andother manufacturing complications. Furthermore, this microstructuralengineering analysis approach, in contrast to the traditionaltrial-and-error, mix-and-test approach, has resulted in the ability todesign hydraulically settable materials with those properties ofstrength, weight, insulation, cost, and environmental neutrality thatare necessary for appropriate food and beverage containers in asignificantly more efficient manner.

The number of different raw materials available to engineer a specificproduct is enormous, with estimates ranging from between fifty thousandand eighty thousand. They can be drawn from such disparately broadclasses as metals, polymers, elastomers, ceramics, glasses, composites,and cements. Within a given class, there is some commonality inproperties, processing, and use-patterns. Ceramics, for instance, have ahigh modulus of elasticity, while polymers have a low modulus; metalscan be shaped by casting and forging, while composites require lay-up orspecial molding techniques; hydraulically settable materials, includingthose made from hydraulic cements, historically have low flexuralstrength, while elastomers have high flexural strength.

However, compartmentalization of material properties has its dangers; itcan lead to specialization (the metallurgist who knows nothing ofceramics) and to conservative thinking ("we use steel because that iswhat we have always used"). It is this specialization and conservativethinking that has limited the consideration of using hydraulicallysettable materials for a variety of products, such as in connection withthe food and beverage industry.

Nevertheless, once it is realized that hydraulically settable materialshave such a wide utility and can be designed and microstructurallyengineered, then their applicability to a variety of possible productsbecomes obvious. Hydraulically settable materials have an additionaladvantage over other conventional materials in that they gain theirproperties under relatively gentle and nondamaging conditions. (Othermaterials require high energy, severe heat, or harsh chemical processingthat significantly affects the material components.) Therefore, manynonhydraulically settable materials can be incorporated intohydraulically settable materials with surprising synergistic propertiesor results if properly designed and engineered.

The design of the compositions of the present invention has beendeveloped and narrowed, first by primary constraints dictated by thedesign, and then by seeking the subset of materials which maximizes theperformance of the components. At all times during the process, however,it is important to realize the necessity of designing products which canbe manufactured in a cost-competitive process.

Primary constraints in materials selection are imposed bycharacteristics of the design of a component which are critical to asuccessful product. With respect to a cup or container for a food andbeverage product, those primary constraints include minimal weight,strength (both compressive and tensile), and toughness requirements,while simultaneously keeping the costs to those comparable to paper,plastic, and metal counterparts.

As discussed above, one of the problems with hydraulically settablematerials in the past has been that they are typically poured into aform, worked, and then allowed to set, harden, and cure over a longperiod of time--even days or weeks. Experts generally agree that ittakes at least one month for traditional concrete products to reach asubstantial degree of their optimum strength. Even with expensive "setaccelerators," this strength gain occurs over a period of days. Suchtime periods are certainly impractical for the economic mass productionof disposable containers and similar products.

As a result, an important feature of the present invention is that whenthe hydraulically settable mixture is molded, it will maintain its shape(i.e., support its own weight subject to minor forces, such as gravityand movement through the processing equipment) in the green statewithout external support. Further, from a manufacturing perspective, inorder for production to be economical, it is important that the moldedcontainer (or sheet used to make a container) rapidly (in a matter ofminutes, or even seconds) achieve sufficient strength so that it can behandled using ordinary manufacturing procedures, even though thehydraulically settable mixture may still be in a green state and notfully hardened.

Another advantage of the microstructural engineering approach of thepresent invention is the ability to develop compositions in whichcross-sections of the structural matrix are more homogeneous than havebeen typically achieved in the prior art. Ideally, when any two givensamples of about 1-2 mm³ of the hydraulically settable structural matrixare taken, they will have substantially similar amounts of voids,aggregates, fibers, any other additives, and properties of the matrix.

In its simplest form, the process of using materials science inmicrostructurally engineering and designing a hydraulically settablematerial comprises characterizing, analyzing, and modifying (ifnecessary): (a) the aggregates, (b) the predicted particle packing, (c)the system rheology, and (d) the processing and energy of themanufacturing system. In characterizing the aggregates, the averageparticle size is determined, the natural packing density of theparticles (which is a function of the size distribution of theparticles) is determined, and the strength of the particles isascertained.

With this information, the particle packing can be predicted accordingto mathematical models. It has been established that the particlepacking is a primary factor for designing desired requirements of theultimate product, such as workability, form stability, shrinkage, bulkdensity, insulative capability, tensile, compressive, and flexuralstrengths, elasticity, durability, and cost optimization. The particlepacking is affected not only by the particle and aggregatecharacterization, but also by the amount of water and its relationshipto the interstitial void volume of the packed aggregates.

System rheology is a function of both macro-theology and micro-rheology.The macro-rheology is the relationship of the solid particles withrespect to each other as defined by the particle packing. Themicro-rheology is a function of the lubricant fraction of the system. Bymodification of the lubricants (which may be water, theology-modifyingagents, plasticizers, or other materials), the viscosity and yieldstress can be chemically modified. The micro-rheology can also bemodified physically by changing the shape and size of the particles,e.g., the use of chopped fibers, plate-like mica, round-shaped silicafume, or crushed rough cement particles will interact with thelubricants differently.

Finally, the manufacturing processing can be modified to manipulate thebalance between workability and form stability. As applied to thepresent invention, this becomes important in significantly increasingthe yield stress during formation of the article of manufacture byeither chemical additive (such as by adding a rheology-modifying agent)or by adding energy to the system (such as by heating the molds).Indeed, it is this discovery of how to manipulate the hydraulicallysettable compositions in order to quickly increase the form stability ofthe compositions during the formation process that make the presentinvention such a significant advancement in the art.

From the following discussion, it will be appreciated how each of thecomponent materials within the hydraulically settable mixture, as wellas the processing parameters, contributes to the primary designconstraints of the food and beverage container so that they can beeconomically mass produced. Specific compositions are set forth in theexamples given later in order to demonstrate how the maximization of theperformance of each component accomplishes the combination of desiredproperties.

B. Food and Beverage Containers.

The term "container" as used in this specification and the appendedclaims is intended to include any article, receptacle, or vesselutilized for storing, dispensing, packaging, or portioning items,whether such use is intended to be short term or long term. Examples ofsuch containers include boxes, cups, jars, bottles, plates, cartons,cases, crates, dishes, egg cartons, lids, straws, cutlery, utensils, orother types of holders. It will be appreciated that in certaincircumstances, the container may seal the contents from the externalatmosphere, and in other circumstances may merely hold or retain theitems.

The term "disposable container" as used in this specification and theappended claims refers to a container which has the characteristicstypically associated with disposable materials. That is, the container(a) is manufactured in such a way that it is economical for thecontainer to be used only once and then discarded, and (b) has aconstruction such that it can be readily discarded or thrown away inconventional waste landfill areas as an environmentally neutral material(without causing significant extraordinary environmental hazards). Theuse of the term "disposable" does not mean that the container mustnecessarily only be a single-use container and that it be discardedafter only one use.

The terms "food" and/or "beverage" are used collectively and are ofteninterchangeably used herein. It is the objective of the presentinvention to develop container products for use with food and beverages.Accordingly, the hydraulically settable materials used in the containersof the present invention have been developed to accommodate the specificneeds of storing, dispensing, packing, and portioning food and beverageproducts. The present invention is of particular use in the "fast-food"industry where disposable cups, plates, trays, platters, and"clam-shell" containers are frequently used to dispense the products.

For purposes of the present invention, the food and beverage containersdisclosed and claimed in the present invention are directed to thosecontainers and materials which come in direct contact with the food orbeverage, including any coating or liner that might be incorporated withthe container. In other words, the present invention is not directed topackaging materials generally, or to containers which hold othercontainers which hold the food or beverage products. Such generalpackaging materials are disclosed in a related patent specification fromwhich priority is claimed above.

The phrases "mass producible" or manufactured in a "commercial" or"economic" manner are intended in the specification and the appendedclaims to refer to a capability of the containers and articles ofmanufacture described herein to be rapidly produced at a rate ofhundreds, thousands, or tens of thousands per hour. The presentinvention is directed to innovative compositions which solve the priorart problems of incorporating hydraulically settable binders into thematrices of products which can be rapidly manufactured by machine,rather than individual hand manufacture of one product at a time (suchas "throwing pots").

The products are intended to be competitive in the marketplace with foodor beverage containers currently made of various materials such aspaper, plastic, polystyrene, or metals. Hence, the articles ofmanufacture of the present invention must be economical to manufacture(typically, the cost will not exceed a few cents per item). Such costrestraints thus require automated production of thousands of thearticles in a very short period of time. Hence, requiring the productsof the present invention to be economically mass produced is asignificant limitation on the qualities of the material and theproducts.

C. Hydraulically Settable Materials

The materials used to manufacture the food and beverage containers ofthe present invention develop strength through the chemical reaction ofwater and a hydraulic binder, such as hydraulic cement, calcium sulfate(or gypsum) hemihydrate, and other substances which harden after beingexposed to water. The term "hydraulically settable materials" as used inthis specification and the appended claims includes any material whosestructural matrix and strength properties are derived from a hardeningor curing of a hydraulic binder. These include cementitious materials,plasters, and other hydraulically settable materials as defined herein.The hydraulically settable binders used in the present invention are tobe distinguished from other cements or binders such as polymerizable,water insoluble organic cements, glues, or adhesives.

The terms "hydraulically settable materials," "hydraulic cementmaterials," or "cementitious materials," as used herein, are intended tobroadly define compositions and materials that contain both ahydraulically settable binder and water, regardless of the extent ofhydration or curing that has taken place. Hence, it is intended that theterm "hydraulically settable materials" shall include hydraulic paste orhydraulically settable mixtures in a green (i.e., unhardened) state, aswell as hardened hydraulically settable or concrete products.

1. Hydraulic Cements

The terms "hydraulically settable binder" or "hydraulic binder" as usedin this specification and the appended claims are intended to includeany inorganic binder such as hydraulic cement, gypsum hemihydrate, orcalcium oxide which develops strength properties and hardness bychemically reacting with water and, in some cases, with carbon dioxidein the air and water. The terms "hydraulic cement" or "cement" as usedin this specification and the appended claims are intended to includeclinker and crushed, ground, milled, and processed clinker in variousstages of pulverization and in various particle sizes.

Examples of typical hydraulic cements known in the art include: thebroad family of portland cements (including ordinary portland cementwithout gypsum), calcium aluminate cements (including calcium aluminatecements without set regulators), plasters, silicate cements (includingβ-dicalcium silicates, tricalcium silicates, and mixtures thereof),gypsum cements, phosphate cements, high alumina cements, microfinecements, slag cements, magnesium oxychloride cements, MDF, "densit-type"cements, and aggregates coated with microfine cement particles.

The term "hydraulic cement" is also intended to include other cementsknown in the art, such as α-dicalcium silicate, which can be madehydraulic under hydrating conditions within the scope of the presentinvention. The basic chemical components of the hydraulic cements withinthe scope of the present invention usually include CaO, SiO₂, Al₂ O₃,Fe₂ O₃, MgO, SO₃, in various combinations thereof. These react togetherin a series of complex reactions to form insoluble calcium silicatehydrates, carbonates (from CO₂ in the air and added water), sulfates,and other salts or products of calcium and magnesium, together withhydrates thereof. The aluminum and iron constituents are thought to beincorporated into elaborate complexes within the above mentionedinsoluble salts. The cured cement product is a complex matrix ofinsoluble hydrates and salts which are complexed and linked togethermuch like stone, and are similarly inert.

Hydraulically settable compositions are typically formed by mixing ahydraulic binder or combinations thereof (such as hydraulic cement) andwater; the resulting mixture may be referred to as a "hydraulic paste"(or "cement paste"). The hydraulic binder and water are mixed eithersimultaneously or subsequently, with some sort of aggregate blended toform a "hydraulically settable mixture." Mortar and concrete areexamples of hydraulically settable mixtures formed by mixing hydrauliccement, water, and some sort of aggregate, suck as sand or rock.

Gypsum is also a hydraulically settable binder that can be hydrated toform a hardened binding agent. One hydratable form of gypsum is calciumsulfate hemihydrate, commonly known as "gypsum hemihydrate." Thehydrated form of gypsum is calcium sulfate dihydrate, commonly known as"gypsum dihydrate." Calcium sulfate hemihydrate can also be mixed withcalcium sulfate anhydride, commonly known as "gypsum anhydrite" orsimply "anhydrite."

Although gypsum binders or other hydraulic binders such as calcium oxideare generally not as strong as hydraulic cement, high strength may notbe as important as other characteristics (e.g., the rate of hardening)in some applications. In terms of cost, gypsum and calcium oxide have anadvantage over hydraulic cement, because they are somewhat lessexpensive. Moreover, in the case where the hydraulically settablematerial contains a relatively high percentage of weak, lighter weightaggregates (such as perlite), the aggregates will often comprise a "weaklink" within the structural matrix. At some point, adding a strongerbinder may be inefficient because the binder no longer contributes itshigher potential strength due to a high content of weaker aggregates.

In addition, gypsum hemihydrate is known to set up or harden in a muchshorter time period than traditional cements. In fact, in use with thepresent invention, it will harden and attain most of its ultimatestrength within about thirty minutes. Hence, gypsum hemihydrate can beused alone or in combination with other hydraulically settable materialswithin the scope of the present invention.

Terms such as "hydrated" or "cured" hydraulically settable mixture,material, or matrix refers to a level of substantial water-catalyzedreaction which is sufficient produce a hydraulically settable producthaving a substantial amount of its potential or final maximum strength.Nevertheless, hydraulically settable materials may continue to hydratelong after they have attained significant hardness and a substantialamount of their final maximum strength.

Terms such as "green" or "green state" are used in conjunction withhydraulically settable mixtures which have not achieved a substantialamount of their final strength, regardless of whether such strength isderived from artificial drying, curing, or other means. Hydraulicallysettable mixtures are said to be "green" or in a "green state" justprior to and subsequent to being molded into the desired shape. Themoment when a hydraulically settable mixture is no longer "green" or ina "green state" is not necessarily a clear-cut line of demarcation,since such mixtures generally attain a substantial amount of their totalstrength only gradually over time. Hydraulically settable mixtures can,of course, show an increase in "green strength" and yet still be"green." For this reason, the discussion herein often refers to the formstability of the hydraulically settable material in the green state.

As mentioned above, preferable hydraulic binders include white cement,portland cement, microfine cement, high alumina cement, slag cement,gypsum hemihydrate, and calcium oxide, mainly because of their low costand suitability for the manufacturing processes of the presentinvention. This list of cements is by no means exhaustive, nor in anyway is it intended to limit the types of binders which would be usefulin making the hydraulically settable containers within the scope of theclaims appended hereto.

The present invention may include other types of cementitiouscompositions such as those discussed in copending patent applicationSer. No. 07/526,231 filed May 18, 1990, now abandoned in the names ofHamlin M. Jennings, Ph.D. and Simon K. Hodson, and entitled"Hydraulically Bonded Cement Compositions and Their Methods ofManufacture and Use," wherein powdered hydraulic cement is placed in anear net final position and compacted prior to the addition of water forhydration. A related continuation-in-part application, now U.S. Pat. No.5,358,676 was filed in the names of Hanlin M. Jennings, Ph.D., Per JustAndersen, Ph.D. and Simon K. Hodson, and also entitled "HydraulicallyBonded Cement Compositions and Their Methods of Manufacture and Use."For purposes of disclosure, the forgoing patents are incorporated hereinby specific reference.

Additional types of hydraulic cement compositions include those whereincarbon dioxide is mixed with hydraulic cement and water. Hydrauliccement compositions made by this method are known for their ability tomore rapidly achieve green strength. This type of hydraulic cementcomposition is discussed in U.S. Pat. No. 5,232,496, in the names ofHamlin M. Jennings, Ph.D. and Simon K. Hodson, and entitled "Process forProducing Improved Building Material and Products Thereof," whereinwater and hydraulic cement are mixed in the presence of a carbonatesource selected from the group consisting of carbon dioxide, carbonmonoxide, carbonate salts, and mixtures thereof. For purposes ofdisclosure, the forgoing patent is incorporated herein by specificreference.

In many situations, it may not be desirable for the food or beveragecontainer to be water soluble. Unfortunately, certain materials whichmight be desirable to incorporate into such containers dissolve inwater. An important advantage of using a hydraulically settable mixtureis that the resulting structural matrix is generally water insoluble (atleast over the period of tinge during which use of the product isintended), which allows it to encapsulate the water soluble aggregatesor other materials added to the hydraulically settable mixture. Hence,an otherwise water soluble component can be incorporated into thegreatly insoluble hydraulically settable matrix and impart itsadvantageous properties and characteristics to the final product.

Nevertheless, in order to design a disposable food or beverage containerwhich will more readily decompose or disintegrate after it has fulfilledits intended use, it may be desirable for the food or beverage containerto break down in the presence of water or moisture. One of theadvantages of the microstructural engineering approach of the presentinvention is the ability to design into the hydraulically settablestructural matrix the desired properties of water resistance orsolubility. In order to obtain a container treat readily decomposes inthe presence of water, it will generally be necessary to decrease theamount of hydraulic binder within the material. Hence, the degree ofwater solubility or insolubility is generally related to theconcentration of hydraulic binder, particularly hydraulic cement, withinthe hydraulically settable mixture. In most cases, adding more hydraulicbinder will make the container less soluble in water.

2. Hydraulic Paste

In each embodiment of the present invention, the hydraulic paste orcement paste is the key constituent which eventually gives the containerthe ability to "set up" and develop strength properties. The term"hydraulic paste" shall refer to a hydraulic binder which has been mixedwith water. More specifically, the term "cement paste" shall refer tohydraulic cement which has been mixed with water. The terms"hydraulically settable," "hydraulic," or "cementitious" mixture shallrefer to a hydraulic cement paste to which aggregates, fibers,rheology-modifying agents, dispersants, or other materials have beenadded, whether in the green state or after it has hardened and/or cured.The other ingredients added to the hydraulic paste serve the purpose ofaltering the properties of the unhardened, as well as the final hardenedproduct, including, but not limited to, strength, shrinkage,flexibility, bulk density, insulating ability, color, porosity, surfacefinish, and texture.

Although the hydraulic binder is understood as the component whichallows the hydraulically settable mixture to set up, to harden, and toachieve much of the strength properties of the material, certainhydraulic binders also aid in the development of better early cohesionand green strength. For example, hydraulic cement particles are known toundergo early gelating reactions with water even before it becomes hard;this can contribute to the internal cohesion of the mixture.

It is believed that aluminates, such as those more prevalent in portlandgrey cement (in the form of tricalcium aluminates) are responsible for acolloidal interaction between the cement particles during the earlierstages of hydration. This in turn causes a level offlocculation/gelation to occur between the cement particles. Thegelating, colloidal, and flocculating affects of such binders has beenshown to increase the moldability (i.e., cohesion and plasticity) ofhydraulically settable mixtures made therefrom.

As set forth more fully below, additives such as fibers andrheology-modifying agents can make substantial contributions to thehydraulically settable materials in terms of tensile, flexural, andcompressive strengths. Nevertheless, even where high concentrations offibers and/or rheology-modifying agents are included and contributesubstantially to the tensile and flexural strengths of the hardenedmaterial, it has been shown that the hydraulic binder neverthelesscontinues to add substantial amounts of compressive strength and otherimportant properties to the final hardened material. In the case ofhydraulic cement, it also substantially reduces the solubility of thehardened material in water.

The percentage of hydraulic binder within the overall mixture variesdepending on the identity of the other added constituents. However, thehydraulic binder is preferably added in an amount ranging from betweenabout 5% to about 90% as a percentage by weight of the wet hydraulicallysettable mixture. From the disclosure and examples set forth herein, itwill be understood that this wide range of weights covers hydraulicallysettable mixtures used to manufacture foam-like, clay-like, orsheet-like materials and containers.

It will be appreciated from the foregoing that embodiments within thescope of the present invention will vary from a very lightweight"foam-like" product to a somewhat higher density "clay-like" product. Inaddition, either foam-like or clay-like materials may first be moldedinto sheets to form a "sheet-like" product, resulting in a product whichcan be handled much like paper, cardboard, plastic, or even a sheet ofmetal. Within these broader categories will be other variations anddifferences which will require varying quantities and identities of thecomponents. The components and their relative quantities maysubstantially vary depending upon the specific container or otherproduct to be made.

Generally, when making a "foam-like" product, it will be preferable toinclude the hydraulic binder within the range from between about 10% toabout 90% by weight of the wet hydraulically settable mixture, and morepreferably within the range from between about 20% to about 50%.

When making a "clay-like" product, it will be preferable to include thehydraulic binder within the range from between about 5% to about 75% byweight of the wet hydraulically settable mixture, more preferably withinthe range from between about 8% to about 60%, and most preferably withinthe range from between about 10b to about 45%.

Finally, when making a "sheet-like" product, it will be preferable toinclude the hydraulic binder within the range from between about 5% toabout 90% by weight of the green hydraulically settable mixture,preferably within the range from about 8% to about 50%, and mostpreferably within the range from about 10% to about 30%.

Despite the foregoing, it will be appreciated that all concentrationsand amounts are critically dependent upon the qualities andcharacteristics that are desired in the final product. For example, in avery thin wall structure (even as thin as 0.05 mm) where strength isneeded, such as in a drinking straw, it may be more economical to have avery high percentage of hydraulic binder with little or no aggregate. Insuch a case, it may also be desirable to include a high amount of fiberto impart flexibility and toughness.

Conversely, in a product in which high amounts of air are incorporated(such as a low density, lightweight, insulating cup), there may be agreater percentage of the rheology-modifying agent, a smaller amount ofcement, and larger amounts of lightweight aggregates. Such materials canhave as high a percentage of air as do polystyrene foam products.

The other important constituent of hydraulic paste is water. Bydefinition, water is an essential component of the hydraulicallysettable materials within the scope of the present invention. Thehydration reaction between hydraulic binder and water yields reactionproducts which give hydraulically settable materials the ability to setup and develop strength properties.

In most applications of the present invention, it is important that thewater-to-cement ratio be carefully controlled in order to obtain ahydraulically settable mixture which after molding, extrusion, and/orcalendering is supporting in the green state. Nevertheless, the amountof water to be used is dependent upon a variety of factors, includingthe types and amounts of hydraulic binder, aggregates, fibrousmaterials, theology-modifying agents, and other materials or additiveswithin the hydraulically settable mixture, as well as the molding orforming process to be used, the specific product to be made, and itsproperties.

The preferred amount of added water within any given application isprimarily dependent upon two key variables: (1) the amount of waterwhich is required to react with and hydrate the binder; (2) the amountof water required to give the hydraulically settable mixture thenecessary rheological properties and workability.

In order for the green hydraulically settable mixture to have adequateworkability water must generally be included in quantities sufficient towet each of the particular components and also to at least partiallyfill the interstices or voids between the particles (including, e.g.,binder particles, aggregates, and fibrous materials) . If water solubleadditives are included, enough water must be added to dissolve orotherwise react with the additive. In some cases, such as where adispersant is added, workability can be increased while using lesswater.

The amount of water must be carefully balanced so that the hydraulicallysettable mixture is sufficiently workable, while at the same timerecognizing that lowering the water content increases both the greenstrength and the final strength of the hardened product. Of course, ifless water is initially included within he mixture, less water must beremoved in order to allow the product to harden.

The appropriate rheology to meet these needs can be defined in terms ofyield stress. The yield stress of the hydraulically settable mixturewill usually be in the range from between about 5 kPa to about 5,000kPa, with the more preferred mixtures having a yield stress within arange from about 100 kPa to about 1,000 kPa, and the most preferredmixtures having a yield stress in the range from about 200 KPa to about700 kPa. The desired level of yield stress can be (and may necessarilyhave to be) adjusted and optimized to the particular molding processbeing used to form the food or beverage container.

In each of the molding processes, it may be desirable to initiallyinclude a relatively high water-to-cement ratio in light of the factthat the excess water can be removed by heating the molded productsduring or shortly after the molding process. One of the importantfeatures of the present invention as compared to the manufacture ofpaper is that the amount of water in the initial mixture is much less;hence, the yield stress is greater for the hydraulically settablemixtures. The result is theft the total amount of water that must beremoved from the initial mixture to obtain a self-supporting material(i.e., a form stable material) is much less in the case of the presentinvention when compared to manufacture of paper.

Nevertheless, one skilled in the art will understand that when moreaggregates or other water absorbing additives are included, a higherwater to hydraulically settable binder ratio is necessary in order toprovide the same level of workability and available water to hydrate thehydraulically settable binder. This is because a greater aggregateconcentration provides a greater volume of interparticulate interstices,or voids, which must be filled by the water. Porous, lightweightaggregates can also internally absorb significant amounts of water dueto their high void content.

Both of the competing goals of greater workability and high greenstrength can be accommodated by initially adding a relatively largeamount of water and then driving off much of the water as steam duringthe molding process, usually by the use of heated molds, rollers, ordrying tunnels.

Based on the foregoing qualifications, typically hydraulically settablemixtures within the scope of the present invention will have awater-to-cement ratio within a range from about 0.1 to about 10,preferably about 0.3 to about 3.5, and most preferably from about 1 toabout 3. The total amount of water remaining after drying the materialto remove excess water will range up to about 10% by weight with respectto the dry, hardened hydraulically settable sheet or container.

It should be understood that the hydraulic binder has an internal dryingeffect on the hydraulically settable mixture because binder particleschemically react with water and reduce the amount of free water withinthe interparticulate interstices. This internal drying effect can beenhanced by including faster reacting hydraulic binders, such as gypsumhemihydrate, along with slower reacting hydraulic cement.

According to a preferred embodiment of the present invention, it hasbeen found desirable that the hydraulic binder and water be mixed in ahigh shear mixture such as that disclosed and claimed in U.S. Pat. No.4,225,247 entitled "Mixing and Agitating Device"; U.S. Pat. No.4,552,463 entitled "Method and Apparatus for Producing a ColloidalMixture"; U.S. Pat. No. 4,889,428 entitled "Rotary Mill"; U.S. Pat. No.4,944,595 entitled "Apparatus for Producing Cement Building Materials";and U.S. Pat. No. 5,061,319 entitled "Process for Producing CementBuilding Material." For purposes of disclosure, the forgoing patents areincorporated herein by specific reference. High shear mixers; within thescope of these patents are available from Khashoggi Industries of SantaBarbara, California, assignee of the present invention.

The use of a high shear mixer has resulted in a more homogeneoushydraulically settable mixture, which has resulted in a product withhigher strength. Furthermore, these high shear mixes can be utilized toentrain significant amounts air into the hydraulically settable mixtureto create "foam-like" products.

C. Rheology-Modifying Agents

The inclusion of a rheology-modifying agent acts increase the plastic orcohesive nature of the hydraulically settable mixture so that it behavesmore like a moldable clay. The rheology-modifying agent tends to thickenthe hydraulically settable mixture by increasing the yield stresswithout greatly increasing the viscosity of the mixture. Raising theyield stress in relation to the viscosity makes the material moreplastic-like and moldable, while greatly increasing the subsequent formstability or green strength.

A variety of natural and synthetic organic rheology-modifying agents maybe used which have a wide range properties, including viscosity andsolubility in water. For example, where it is desirable for thecontainer to more quickly break down into environmentally benigncomponents, it may be preferable to use a rheology-modifying agent whichis more water soluble. Conversely, in order to design a material capableof withstanding prolonged exposure to water, it may be preferable to usea rheology-modifying agent which is less soluble in water or to use ahigh content of the hydraulic binder with respect to therheology-modifying agent.

The various rheology-modifying agents contemplated by the presentinvention can be roughly organized into the following categories: (1)polysaccharides and derivatives thereof, (2) proteins and derivativesthereof, and 3) synthetic organic materials. Polysacchariderheology-modifying agents can be further subdivided into (a)cellulose-based materials and derivatives thereof, (b) starch-basedmaterials and derivatives thereof, and (c) other polysaccharides.

Suitable cellulose-based rheology-modifying agents include, for example,methylhydroxyethylcellulose, hydroxymethylethylcellulose,carboxymethylcellulose, methylcellulose, ethylcellulose,hydroxyethylcellulose, hydroxyethylpropylcellulose, etc. The entirerange of possible permutations is enormous and shall not be listed here,but other cellulose materials which have the same or similar propertiesas these would also work well.

Suitable starch-based materials include, for example, amylopectin,amylose, seagel, starch acetates, starch hydroxyethylethers, ionicstarches, long-chain alkylstarches, dextrins, amine starches, phosphatesstarches, and dialdehyde starches.

Other natural polysaccharide-based rheology-modifying agents include,for example, alginic acid, phycocolloids, agar, gum arabic, guar gum,locust bean gum, gum karaya, and gum tragacanth.

Suitable protein-based rheology-modifying agents include, for example,Zein® (a prolamine derived from corn), collagen (derivatives extractedfrom animal connective tissue such as gelatin and glue), and casein (theprinciple protein in cow's milk).

Finally, suitable synthetic organic plasticizers include, for example,polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol,polyvinylmethyl ether, polyacrylic acids, polyacrylic acid salts,polyvinyl acrylic acids, polyvinyl acrylic acid salts, polyacrylimides,ethylene oxide polymers, polylactic acid, and latex, which is astyrenebutadiene copolymer.

The rheology of polylactic acid is significantly modified by heat andcould be used alone or in combination with any other of the foregoingrheology-modifying agents.

A currently preferred rheology-modifying agent ismethylhydroxyethylcellulose, examples of which are Tylose® FL 15002 andTylose® 4000, both of which are available from HoechstAktiengesellschaft of Frankfurt, Germany. Lower molecular weightrheology-modifying agents such as Tylose® 4000 can act to plasticize themixture rather than thicken it, which helps during extrusion or rollingprocedures.

More particularly, lower molecular weight rheology-modifying agentsimprove the internal flow of the hydraulically settable mixture duringmolding processes by lubricating the particles. This reduces thefriction between the particles as well as between the mixture and theadjacent mold surfaces. Although a methylhydroxyethylcelluloserheology-modifying agent is preferred, almost any non-toxicrheology-modifying agent (including any listed above) which imparts thedesired properties would be appropriate.

Another preferred rheology-modifying agent that can be used instead of,or in conjunction with, Tylose® is polyethylene glycol having amolecular weight of between 20,000 and 35,000. Polyethylene glycol worksmore as a lubricant and adds a smoother consistency to the mixture. Forthis reason, polyethylene glycol might be referred more precisely as a"plasticizer." In addition, it gives the molded hydraulically settablematerial a smoother surface. Finally, polyethylene glycol can create acoating around soluble components of the mixture and thereby render thehardened product less water soluble.

Finally, starch-based rheology-modifying agents are of particularinterest within the scope of the present invention because of theircomparatively low cost compared to cellulose-based theology-modifyingagents such as Tylose®. Although starches typically require heat and/orpressure in order to gelate, starches may by modified and prereacted sothat they can gel at room temperature. The fact that starches, as wellas many of the other rheology-modifying agents listed above, have avariety of solubilities, viscosities, and rheologies allows for thecareful tailoring of the desired properties of a mix design so that itwill conform to the particular manufacturing and performance criteria ofa particular food or beverage container.

The rheology-modifying agent within the hydraulically settable materialsof the present invention can be included in an amount up to about 50% byweight of the mixture. Generally, however, the preferable concentrationis up to about 20%, with less than about 10% being more preferable.

D. Aggregates

Aggregates common in the concrete industry may be used in thehydraulically settable mixtures of the present invention, except thatthey often must be more finely ground due to the size limitationsimposed by the generally thin-walled structures of the presentinvention. The diameter of the aggregates used will most often be lessthan about 30% of the cross-section of the structural matrix of thecontainer.

Aggregates may be added to increase the strength, decrease the costs byacting as a filler, decrease the weight, and/or increase the insulationability of the resultant hydraulically settable materials. Aggregates,particularly plate-like aggregates, are also useful for creating asmooth surface finish.

Examples of useful aggregates include perlite, vermiculite, sand,gravel, rock, limestone, sandstone, glass beads, aerogels, xerogels,seagel, mica, clay, synthetic clay, alumina, silica, fly ash, silicafume, tabular alumina, kaolin, microspheres, hollow glass spheres,porous ceramic spheres, gypsum dihydrate, calcium carbonate, calciumaluminate, cork, seeds, lightweight polymers, xonotlite (a crystallinecalcium silicate gel), lightweight expanded clays, unreacted cementparticles, pumice, exfoliated rock, and other geologic materials.

Unreacted cement particles may also be considered to be "aggregates" inthe broadest sense of the term. Even discarded hydraulically settablematerials, such as discarded sheets, containers, or other objects of thepresent invention can be employed as aggregate fillers andstrengtheners. It will be appreciated that the containers of the presentinvention can be effectively recycled.

Both clay and gypsum are particularly important aggregate materialsbecause of their ready availability, extreme low cost, workability, easeof formation, and because they can also provide a degree of binding andstrength if added in high enough amounts. Clay is a general term used toidentify essentially all earths that form a paste with water and hardenwhen dried. The predominant clays include silica and alumina (used formaking pottery, tiles, brick, and pipes) and kaolinite. The kaolinicclays are anauxite, which has the chemical formula Al₂ O₃.SiO₂.H₂ O, andmontmorilonite, which has the chemical formula Al₂ O₃.SiO₂.H₂ O.However, clays may contain a wide variety of other substances, such asiron oxide, titanium oxide, calcium oxide, calcium oxide, zirconiumoxide, and pyrite.

In addition, although clays have been used for millennia and can obtainhardness even without being fired, such unfired clays are vulnerable towater degradation and exposure, are extremely brittle, and have lowstrength. Nevertheless, clay makes a good, inexpensive aggregate withinthe hydraulically settable structural matrix.

Similarly, gypsum hemihydrate is also hydratable and forms the dihydrateof calcium sulfate in the presence of water. Thus, gypsum may exhibitthe characteristics of both an aggregate and a binder depending onwhether (and the concentration of) the hemihydrate or dihydrate form isadded to a hydraulically settable mixture.

Examples of aggregates which can add a lightweight characteristic to thecementitious mixture include perlite, vermiculite, glass beads, hollowglass spheres, calcium carbonate, synthetic materials (e.g., porousceramic spheres, tabular alumina, etc.), cork, lightweight expandedclays, sand, gravel, rock, limestone, sandstone, pumice, and othergeological materials.

In addition to conventional aggregates used in the cement industry, awide variety of other aggregates, including fillers, strengtheners,metals and metal alloys (such as stainless steel, calcium aluminate,iron, copper, silver, and gold), balls or hollow spherical materials(such as glass, polymeric, and metals), filings, pellets, powders (suchas microsilica), and fibers (such as graphite, silica, alumina,fiberglass, polymeric, organic fibers, and other such fibers typicallyused to prepare various types of composites), may be combined with thehydraulic cements within the scope of the present invention. Evenmaterials such as seeds, starches, gelatins, and agar-type materials canbe incorporated as aggregates in the present invention.

From the foregoing, it will be understood that the amount of aparticular aggregate within a mixture will vary depending upon thedesired performance criteria of a particular food or beverage container.There are many situations when little or no aggregate will be used.However, in most situations, the aggregate will be included in an amountof up to about 80% by weight of the green or wet hydraulic settablemixture.

In the products contemplated by the present invention where highinsulation is desired, the amount of lightweight aggregate will usuallybe within the range from between about 3% to about 50% by weight, andmost preferably, within the range from about 20% to about 35% by weightof the green mixture. Heavier weight aggregates will also be included inroughly the same amounts, albeit in lower quantities per unit of mass.

Further, it will be appreciated that for any given product, certain ofthese aggregates may be preferable while others may not be usable. Forexample, certain of the aggregates may contain harmful materials that,for some uses, could leach from the hydraulically settable mixture;nevertheless, most of the preferred materials are not only nontoxicunder most uses in the food and beverage industry, but they are alsomore environmentally neutral than the components in existing disposableproducts.

Fibrous aggregates are used in the present invention primarily to modifythe weight characteristics of the cementitious mixture, to add formstability to the mixture, and to add strength and flexibility to theresulting cementitious matrix, although certain fibers may also impartsome level of insulation to the final product. Therefore, the term"aggregates" will refer to all other filler materials, which arenonfibrous, and whose function is mainly to impart strength,rheological, textural, and insulative properties to the materials.

It is often preferable, according to the present invention, to include aplurality of differently sized and graded aggregates capable of morecompletely filling the interstices between the aggregate and hydraulicbinder particles. Optimizing the particle packing density reduces theamount of water necessary to obtain adequate workability by eliminatingspaces which would otherwise be filled with interstitial water, oftenreferred to as "capillary water." In addition, using less waterincreases the strength of the final hardened product (according to theFeret Equation).

In order to optimize the packing density, differently sized aggregateswith particle sizes ranging from as small as about 0.5 μm to as large asabout 2 mm may be used. (Of course, the desired purpose and thickness ofthe resulting product will dictate the appropriate particle sizes of thevarious aggregates to be used.) It is within the skill of one in the artto know generally the identity and sizes of the aggregates to be used inorder to achieve the desired characteristics in the final hydraulicallysettable article or container.

In certain preferred embodiments of the present invention, it may bedesirable to maximize the amount of the aggregates within thehydraulically settable mixture in order to maximize the properties andcharacteristics of the aggregates (such as qualities of strength, lowdensity, or high insulation). The use of particle packing techniques maybe employed within the hydraulically settable material in order tomaximize the amount of the aggregates.

A detailed discussion of particle packing can be found in the followingarticle coauthored by one of the inventors of the present invention:Johansen, V. & Andersen, P. J. "Particle Packing and ConcreteProperties," Materials of Concrete II at 111-147, The American CeramicSociety (1991). Further information is available in the DoctoralDissertation of Anderson, P. J., "Control and Monitoring of ConcreteProduction--A Study of Particle Packing and Rheology," The DanishAcademy of Technical Sciences. The advantages of such packing of theaggregates can De further understood by reference to the examples whichfollow in which hollow glass spheres of varying sizes are mixed in orderto maximize the amount of the glass balls in the hydraulically settablemixture.

In embodiments in which it is desirable to obtain a food or beveragecontainer with high insulation capability, it may be preferable toincorporate into the hydraulically settable matrix a lightweightaggregate which has a low thermal conductivity, or "k-factor" (definedas W/m·K). The k-factor is roughly the reciprocal of the expressioncommonly used in the United States to describe the overall thermalresistance of a given material, or "R-factor," which is generallydefined as having units of hr·ft² °F./BTU. The term R-factor is mostcommonly used in the United States to describe the overall thermalresistance of a given material without regard to the thickness of thematerial. However, for purposes of comparison, it is common to normalizethe R-factor to describe thermal resistance per inch of thickness of thematerial in question or hr·ft² °F./BTU·in.

For purposes of this specification, the insulating ability of a givenmaterial will hereinafter be expressed only in terms of the IUPAC methodof describing thermal conductivity, i.e., "k-factor." (The conversion ofthermal resistance expressed in British units (hr·ft² °F./BTU·in) toIUPAC units can be performed by multiplying the normalized number by6.9335 and then taking the reciprocal of product.) Generally, aggregateshaving a very low k-factor also contain large amounts of trappedinterstitial space, air, mixtures of gases, or a partial vacuum whichalso tends greatly reduce the strength of such aggregates. Therefore,concerns for insulation and strength tend to compete and should becarefully balanced when designing a particular mixed design.

The preferred insulating, lightweight aggregates include expanded orexfoliated vermiculite, perlite, calcined diatomaceous earth, and hollowglass spheres--all of which tend to contain large amounts ofincorporated interstitial space. However, this list is in no wayintended to exhaustive, these aggregates being chosen because of theircost and ready availability. Nevertheless, any aggregate with a lowk-factor, which is able to impart sufficient insulation properties intothe cementitious food container, is within the purview of the presentinvention.

E. Fibers

As used in the specification and the appended claims, the terms "fibers"and "fibrous materials" include both inorganic fibers and organicfibers. Fibers are a particular kind of aggregate which may be added tothe hydraulically settable mixture to increase the cohesion, elongationability, deflection ability, toughness, fracture energy, flexural,tensile and, on occasion, compressive strengths of the resultinghydraulically settable material. Fibrous materials reduce the likelihoodthat the hydraulically settable container will shatter when a strongcross-sectional force is applied.

Fibers which may be incorporated into the structural matrix arepreferably naturally occurring fibers, such as cellulosic fibersextracted from hemp, cotton, plant leaves, wood or stems, or fibers madefrom glass, silica, ceramic, or metal. Glass fibers are preferablypretreated to be alkali resistant.

Preferred fibers of choice include glass fibers, abaca, bagasse, woodfibers (both hard wood or soft wood, such as southern pine), and cotton.Recycled paper fibers can be used, but they are somewhat less desirablebecause of the fiber disruption that occurs during the original papermanufacturing process. Any equivalent fiber, however, which impartsstrength and flexibility is also within the scope of the presentinvention. Abaca fibers are available from Isarog Inc. in thePhilippines. Glass fibers, such as Cemfill® are available fromPilkington Corp. in England.

These fibers are preferably used in the present invention due to theirlow cost, high strength, and ready availability. Nevertheless, anyequivalent fiber which imparts compressive and tensile strength, as wellas toughness and flexibility (if needed), is certainly within the scopeof the present invention. The only limiting criteria is that the fibersimpart the desired properties without adversely reacting with the otherconstituents of the hydraulic material and without contaminatingfoodstuffs stored or dispensed in the containers containing such fibers.

The fibers used to make the food and beverage containers of the presentinvention preferably have a high length to width ratio (or "aspectratio") because longer, narrower fibers can impart more strength to thestructural matrix without significantly adding bulk and mass to themixture. The fibers should have an aspect ratio of at least about 10:1,preferably at least about 100:1, and most preferably at least about200:1.

Preferred fibers should also have a length that is several times thediameter of the hydraulic binder particles. Fibers having a length thatis at least twice the length of the hydraulic binder particles willwork; fibers having an average length that is at least 10 times thediameter of the hydraulic binder particles are preferred, with at least100 times being more preferred, and even 1000 times being very useful.

The amount of fibers added to the hydraulically settable mixture matrixwill vary depending upon the desired properties of the final product,with strength, toughness, flexibility, and cost being the principlecriteria for determining the amount of fiber to be added in any mixeddesign. In most cases, fibers will be added in the amount within therange from about 0.2% to about 50% by volume of the hardenedhydraulically settable mixture, more preferably within the range fromabout 1% to about 30% by volume, and most preferably within the rangefrom about 5% to about 15% by volume.

It will be appreciated, however, that the strength of the fiber is avery important feature in determining the amount of the fiber to beused. The stronger the tensile strength of the fiber, the less theamount that must be used to obtain the same tensile strength in theresulting product. Of course, while some fibers have a high tensilestrength, other types of fibers with a lower tensile strength may bemore elastic. Hence, a combination of two or more fibers may bedesirable in order to obtain a resulting product that maximizes multiplecharacteristics, such as high tensile strength and high elasticity.

It should be understood that the fibers used within scope of the presentinvention differ from fibers typically employed in making paper orcardboard products, primarily in the way in which the fibers areprocessed. In the manufacture of paper, either a Kraft or a sulfiteprocess is typically used to form the pulp sheet. In the Kraft process,the fibers are "cooked" in a NaOH process to break up the fibers. In asulfite process, acid is used in the fiber disintegration process.

In both of these processes, the fibers are first processed in order torelease lignins locked within the fiber walls. However, in order torelease the lignins from the fiber, some of the strength of the fiber islost. Because the sulfite process is even more severe, the strength ofthe paper made by a sulfite process will generally have only about ofthe strength of paper made by the Kraft process. (Hence, to the extentwood fibers are included, those processed using a Kraft process would bepreferred.)

Once the wood has been made into wood pulp by either a Kraft or asulfite process, it is further processed in a beater in order to furtherrelease lignins and hemicellulose within the fibers and also to fray thefibers. A slurry generally containing 99.5% water and 0.5% wood pulp issubjected to heavy beating in order to release enough hemicellulose andfray the fibers sufficiently to form a fibrous mixture that isessentially self-binding through an intertwining web effect between thefibers.

The fibers are essentially self-binding through a web effect of thefrayed fiber ends and the adhesive ability of the released lignins andhemicellulose, as well as :he hydrogen bonding between the fibers.Hence, "web physics" and hydrogen bonding govern the forces maintainingthe integrity of the resultant paper or cardboard product. However, thecost of such harsh treatment is that the fibers develop major flawsalong the entire length of the fiber, thereby resulting in a loss ofmuch of their tensile, tear, and burst strengths.

In contrast, the fibers within the scope of the present inventionundergo no such harsh treatment from the beater and, is therefore,retain most of their initial strength. This is possible because they arebound together using a hydraulic binder. Hence, matrix to fiber adhesionrather than web physics forces are chiefly responsible for maintainingthe integrity of the products of the present invention.

Consequently, far less fiber may be added to the hydraulically settablemixtures of the present invention while still deriving a high level ofstrength from the fibers. Employing less fiber while maintaining goodstrength properties allows a more economically produced sheet orcontainer (as compared to paper) because (1) fiber is typically far moreexpensive than either the hydraulic binder or the aggregates, and (2)the capital investment for the processing equipment is much less.

It should also be understood that some fibers, such as southern pine andabaca, have high tear and burst strengths, while others, such as cotton,have lower strength but greater flexibility. In the case where bothflexibility and high tear and burst strength is desired, a mixture offibers having the various properties can be added to the mixture.

F. Dispersants

The term "dispersant" is used herein to refer to the class of materialswhich can be added to reduce the viscosity and yield stress of thehydraulically settable mixture. A more detailed description of the useof dispersants may be found in the Master's Thesis of Andersen, P. J.,"Effects of Organic Superplasticizing Admixtures and their Components onZeta Potential and Related Properties of Cement Materials" (1987).

Dispersants generally work by being adsorbed onto the surface of thehydraulic binder particles and/or into the near colloid double layer ofthe binder particles. This creates a negative charge on or around thesurfaces of the particles, causing them to repel each other. Thisrepulsion of the particles adds "lubrication" by reducing the frictionor attractive forces that would otherwise cause the particles no havegreater interaction. Hence, less water can be added initially whilemaintaining the workability of the hydraulically settable mixture.

Greatly reducing the viscosity and yield stress may be desirable whereplastic-like properties, cohesiveness, and/or form stability are lessimportant. Adding a dispersant aids in keeping the hydraulicallysettable mixture workable even when very little water is added,particularly where there is a "deficiency" of water. Hence, adding adispersant allows for an even greater deficiency of water, although themolded sheet or container may have somewhat less form stability if toomuch dispersant is used. Nevertheless, including less water initiallywill theoretically yield a stronger final cured product according to theFeret Equation.

Whether or not there is a deficiency of water is both a function of thestoichiometric amount of water required to hydrate the binder and theamount of water to occupy the interstices between the particles in thehydraulically settable mixture, including the hydraulic binder particlesthemselves, the particles within the aggregate material, and/or thefibrous material. As stated above, particle packing reduces the volumeof the interstices between the hydraulic binder and aggregate particlesand, therefore, the amount of water necessary to fully hydrate thebinder and maintain the workability of the hydraulically settablemixture by filling the interstitial space.

However, due to the nature of the coating mechanism the dispersant, theorder in which the dispersant is added the mixture is often critical. Ifa flocculating/gelating agent such as Tylose® is added, the dispersantmust be added first and the flocculating agents second. Otherwise, thedispersant will not be able to become adsorbed on the surface of thehydraulic binder particles, as the Tylose® will be irreversibly adsorbedto form a protective colloid on the surface, thereby preventing thedispersant from being adsorbed.

A preferred dispersant is sulfonated naphthalene-formaldehydecondensate, an example of which is WRDA 19, which is available from W.R. Grace, Inc., located in Baltimore. Other dispersants which would workwell include sulfonated melamine-formaldehyde condensate,lignosulfonate, and polyacrylic acid.

The amount of added dispersant will generally range up to about 5% byweight of the hydraulic binder, more preferably within the range ofbetween about 0.2% to about 4%, and most preferably within a range ofbetween about 0.5% to about However, it is important not to include toomuch dispersant, as it tends to retard the hydration reactions between,e.g., hydraulic cement and water. Adding too much dispersant can, infact, prevent hydration, thereby destroying the binding ability of thecement paste altogether.

The dispersants contemplated within the present invention have sometimesbeen referred to in the concrete industry as "superplasticizers." Inorder to better distinguish dispersants from rheology-modifying agents,which often act as plasticizers, the term "superplasticizer" will not beused in this specification.

G. Air Voids

Where insulation, not strength, is the overriding factor (i.e., whetherit is desired to insulate hot or cold materials), it may be desirable toincorporate tiny air voids within the hydraulically settable structuralmatrix of the containers in addition to, or in place of, lightweightaggregates in order to increase the container's insulating properties.The incorporation of air voids into the cementitious mixture iscarefully calculated to impart the requisite insulation characteristicswithout degrading the strength of the container to the point ofnonutility. Generally, however, if insulation is not an importantfeature of a particular product, it is desirable to minimize any airvoids in order to maximize strength and minimize volume.

In certain embodiments, nonagglomerated air voids may be introduced byhigh shear, high speed mixing of the hydraulically settable mixture,with a foaming or stabilizing agent added to the mixture to aid in theincorporation of air voids. The high shear, high energy mixers discussedabove are particularly useful in achieving this desired goal. Suitablefoaming and air entraining agents include commonly used surfactants. Onecurrently preferred surfactant is a polypeptide alkylene polyol, such asMearlcrete® Foam Liquid.

In conjunction with the surfactant, it will be necessary to stabilizethe entrained air within the material using a stabilizing agent likeMearlcel 3532®, a synthetic liquid anionic biodegradable solution. BothMearlcrete® and Mearlcel® are available from the Mearl Corporation inNew Jersey. Another foaming and air-entraining agent is vinsol resin.Inaddition, the theology-modifying agent can act to stabilize theentrained air. Different air-entraining agents and stabilizing agentsimpart different degrees of foam stability to the hydraulically sortablemixture, and they should chosen in order to impart the properties thatare best suited for a particular manufacturing process.

During the entrainment of air, the atmosphere above the high speed mixercan be saturated with a gas such as carbon dioxide, which has been foundto cause an early false setting and create form and foam stability ofthe hydraulically settable mixture. The early false setting and foamstability is thought to result from the reaction of CO₂ and hydroxideions within the hydraulically sortable mixture to form soluble sodiumand potassium carbonate ions, which in turn can interact with thealuminate phases in the cement and accelerate the setting of themixture.

Foam stability helps maintain the dispersion, and prevents theagglomeration, of the air voids within the uncured hydraulicallysettable mixture. Failure to prevent the coalescence of the air voidsactually decreases the insulation effect, and it also greatly decreasesthe strength of the cured hydraulically settable mixture. Raising thepH, increasing the concentration of soluble alkali metals such as sodiumor potassium, adding a stabilizing agent such as a polysacchariderheology-modifying agent, and carefully adjusting the concentrations ofsurfactant and water within the hydraulically settable mixture all helpto increase the foam stability of the mixture.

During the process of molding and/or hardening the hydraulicallysettable mixture, it is often desirable to heat up the hydraulicallysettable mixture in order to increase the volume of the air void system.Heating also aids in rapidly removing significant amounts of the waterfrom the hydraulically settable mixture, thereby increasing the greenstrength of the molded product.

If a gas has been incorporated into the hydraulically settable mixture,heating the mixture to 250° C., for example, will result (according tothe ideal gas equation) in the gas increasing its volume by about 85%.When heating is appropriate, it has been found desirable for the heatingto be within a range from about 100° C. to about 250° C. Moreimportantly, if properly controlled, heating will not result in thecracking of the structural matrix of the container or yieldimperfections in the surface texture of the container.

In other applications, where viscosity of the hydraulically settablemixture is high, such as is required in certain molding processes, it ismuch more difficult to obtain adequate numbers of air voids through highshear mixing. In this case, air voids may alternatively be introducedinto the hydraulically settable mixture by adding an easily oxidizedmetal, such as aluminum, magnesium, zinc, or tin into a hydraulicmixture that is either naturally alkaline (such as a hydraulic cement orcalcium oxide containing mixture) or one that has been made alkaline(such as those containing gypsum or another alkaline hydraulic binder).

This reaction results in the evolution of tiny hydrogen bubblesthroughout the hydraulically settable mixture. Adding a base such assodium hydroxide to, and/or heating (as described below), thehydraulically settable mixture increases the rate of hydrogen bubblegeneration.

It may further be desirable to heat the mixture in order to initiate thechemical reaction and increase the rate of formation of hydrogenbubbles. It has been found that heating the molded product totemperatures in the range of from about 50° C. to about 100° C., andpreferably from about 75° C. to about 85° C., effectively controls thereaction and also drives off a significant amount of the water. Again,this heating process does not result in the introduction of cracks intothe matrix of the molded product. This second method of introducing airvoids into the structural matrix can be used in conjunction with, or inplace of, the introduction of air through high speed, high shear mixingin the case of low viscosity hydraulic mixtures used in some moldingprocesses.

Finally, air voids may be introduced into the hydraulically settablemixture during the molding process by adding a blowing agent to themixture, which will expand when heat is added to the mixture. Blowingagents typically consist low boiling point liquid and finely dividedcalcium carbonate (chalk). The chalk and blowing agent are uniformlymixed into the hydraulically settable mixture and kept under pressurewhile heated. The liquid blowing agent penetrates into the pores of theindividual chalk particles, which act as points from which the blowingagent can then be vaporized upon thermal expansion of the blowing agentas the pressure is suddenly reduced.

During the molding or extrusion process, the mixture is heated while atthe same time it is compressed. While the heat would normally cause theblowing agent to vaporize, the increase in pressure prevents the agentfrom vaporizing, thereby temporarily creating an equilibrium. When thepressure is released after the molding or extrusion of the material, theblowing agent vaporizes, thereby expanding or "blowing" thehydraulically settable material. The hydraulically settable materialeventually hardens with very finely dispersed voids throughout thestructural matrix. Water can also act as a blowing agent as long as themixture is heated above the boiling point of water and kept underpressure of up to 50 bars.

Air voids increase the insulative properties of the hydraulicallysettable containers and also greatly decrease the bulk density and,hence, the weight of the final product. This reduces the overall mass ofthe resultant product, which reduces the amount of material that isrequired for the manufacture of the containers and which reduces theamount of material that will ultimately be discarded in the case ofdisposable containers.

It has also been discovered that, after the cementitious container hassolidified, many of the compositional designs of the present inventionresult in a matrix that is slightly permeable, especially to tinyhydrogen gas molecules, which can diffuse out of the structural matrix.This breatheability factor is highly desirable of certain types of foodcontainers, such as the "clam-shell" containers used in the fast foodindustry, so that bread products do not become soggy.

H. Set Accelerators

In some cases it may be desirable to accelerate the initial set of thehydraulically settable mixture by adding to the mixture an appropriateset accelerator. These include Na₂ CO₃, KCO₃, KOH, NaOH, CaCl₂, CO₂,triethanolamine, aluminates, and the inorganic alkali salts of strongacids, such as HCl, HNO₃, and H₂ SO₄. In fact, any compound whichincreases the solubility of gypsum and calcium hydroxide will tend toaccelerate the initial set of hydraulically settable mixtures,particularly cementitious mixtures.

The amount of set accelerator which may be added to a particularhydraulically settable mixture will depend upon the degree of setacceleration that is desired. This in turn will depend on a variety offactors, including the mix design, the time interval between the stepsof mixing the components and molding the hydraulically settable mixture,the temperature of the mixture, and the identity of the accelerator. Oneof ordinary skill in the art will be able to adjust the amount of addedset accelerator according to the parameters of a particularmanufacturing process in order to optimize the setting time of thehydraulically settable mixture.

I. Coatings

Each of the component materials within the containers is essentiallyharmless to humans and animals. However, it is within the scope of thepresent invention to coat the hydraulically settable food and beveragecontainers with sealing materials and other protective coatings. Onesuch coating is calcium carbonate, which also allows the printing ofindicia on the surface of the containers. Other coatings which might beappropriate include hydroxypropylmethylcellulose, polyethylene glycol,kaolin clay, acrylics, acrylates, polyurethanes, melamines,polyethylene, polylactic acid, synthetic polymers, and waxes (such asbeeswax petroleum based wax). In some cases, it may be preferable forthe coating to be elastomeric, deformable, or waterproof. Some coatingsmay also be used to strengthen places where the hydraulically settablematerial may be severely bent, such as the hinge of a box or"clam-shell" container. In such cases, a pliable, possibly elastomeric,coating may be preferred. Besides these coatings, any FDA approvedcoating material would work depending on the application involved.

For example, an FDA-approved coating comprised of sodium silicate, whichis acid resistant, is a particularly useful coating. Resistance toacidity is important, for example, where the container is exposed tofoods or drinks having a high acid content, such as soft drinks orjuices. Where it is desirable to protect the container from basicsubstances, the containers can be coated with an appropriate polymer orwax, such as are used to coat paper containers.

In some applications, such as in the case of warm, moist food, it isimportant that the coating allow the container to "breathe," or bepermeable to water molecules, while still maintaining its ability tokeep the steamy food product fairly insulated. In other words, in a"breathable" container, water cannot pass through the wall of thecontainer, but water vapor can. Such a breatheability feature isimportant when serving certain food products, such as burgers, so thatthe bun does not become soggy.

Another type of coating that may be placed on surface of the containersof the present invention is a reflective coating for reflecting heatinto or out of the container. Such reflective coatings are well known inthe art, although their applicability to hydraulically settablecontainers is novel.

II. Specific Applications of the Materials into Containers

The key structural component which gives strength to the food orbeverage containers of the present invention is the hydraulicallysettable structural matrix. Within the basic matrix formed by thereaction products of the hydraulic binder and water are incorporatedother components (such as fibers, aggregates, air voids,theology-modifying agents, dispersants, and even accelerants), which addadditional characteristics and properties including strength properties.

A. Purposes of the Components within Hydraulically Settable Mixtures

As discussed above, fibers are added to impart particular tensilestrength and toughness to the hydraulically settable container;sometimes, the fibers can contribute to the insulating capabilities ofthe article of manufacture. In the case of insulating and/or lightweightcontainers, aggregates are employed to increase the insulation abilityand decrease the bulk specific gravity of the hydraulically set tablecontainers. In addition, discontinuous, finely dispersed air voids canbe mechanically or chemically introduced into the hydraulically settablemixture to assist or take the place of lightweight aggregates.

In the case where low weight and high insulation are less important, orwhere a dense product having greater compressive strength isspecifically desired, heavier weight (and less expensive) aggregates,such as finely ground sand or limestone, can be added to increase thebulk and decrease the cost of the hydraulically settable material. Asdisclosed elsewhere, the choice of the aggregate can be very importantto determining the surface finish and texture of the resultant product.Smooth glossy finishes can be obtained by adding "plate-like" aggregates(such as mica), while rougher textures can be obtained with coarsersand.

Because this invention is directed toward containers which are intendedto come into contact with foodstuffs, the materials within thecontainers must not contain, or impart into the food or beveragestherein, any hazardous substances. The typical hydraulic binders,aggregate material, and fibers used in the present invention meet thisrequirement. The preferred hydraulic cements that can be used hereincontain differing quantities of the following compounds beforehydration: CaO, SiO₂, Al₂ O₃, Fe₂ O₃, MgO, and SO₃. Upon hydration,these react to form very stable, rocklike compounds, which areessentially harmless to humans and animals.

In particular, upon hydration these substances are tightly bound incrystalline phases, which are largely water insoluble. Such crystallinephases have been classified as follows:

alite tricalcium silicate (3CaO.SiO₂, or C₃ S)

belite: dicalcium silicate (2CaO.SiO₂ or C₂ S)

celite: tricalcium aluminate (3CaO.Al₂ O₃ or C₃ A) and tetracalciumaluminum ferrate (4CaO.Al₂ O3.Fe₂ O₂ or C₄ AF)

These calcium silicates are only slightly water soluble over time.

The fibers used herein are preferably natural organic fibers derivedfrom plant material, but they may also be inert inorganic fibers such asglass fibers. Either type of fiber is harmless to humans and animals.

The aggregates are preferably small, lightweight rocklike substances; inmany cases, these materials will preferably contain a high percentage ofair voids, which may occur naturally or be imparted into the material byknown processing techniques. Like hydrated cement, these aggregates inthe specific parameters of this application are also inert, very stable,unreactive, and harmless to humans and animals.

The size of the aggregates may be controlled in order to optimize theparticle packing density in order to maximize the desirable propertiesand characteristics of the aggregates with the hydraulically settablemixture. Simply stated, particle packing techniques maximize the amountof the aggregates within the matrix and minimize the space (and hencediscontinuities) between the aggregates. This allows for greaterworkability with the addition of less water, which ultimately results inan easier, faster, and, thus, less expensive drying process, as well asa stronger hardened structural matrix within the food or beveragecontainer.

The discontinuous voids which are chemically introduced into thestructural matrix are most likely to be filled with air after thehydrogen diffuses out of the matrix. (As taught elsewhere, othersimilarly safe gases can be used in the manufacturing process.) Contrastthis with polystyrene foam containers, wherein the air pockets withinthe formed matrix might contain harmful CFCs or other gaseous blowingagents involved in the manufacture of polystyrene. Likewise, bleachedpaper products may be impregnated with tiny quantities of dioxin, asdiscussed above.

The hydraulically settable containers within the scope of the presentinvention can be characterized as being lightweight, yet retainingsufficient strength for the desired purpose. Preferably, foam-likecompositions of the present invention will have a bulk density of lessabout 0.7 g/cm³, clay-like compositions less than about 0.7 g/cm³, andsheet-like compositions less than about 1.2 g/cm³.

Typically, the hydraulically settable containers will have a tensilestrength to bulk density ratio in the range from about 1 MPa·cm³ /g toabout 300 MPa·cm³ /g. In the preferred embodiments, the tensile strengthto bulk density ratio will usually be in the range from about 2 MPa·cm³/g to about 60 MPa-cm³ /g, with the more preferred range being fromabout 3 MPa·cm³ /g to about 30 MPa·cm³ /g.

A significant advantage of the hydraulically settable containersaccording to the present invention is that they do not require, orresult in, the emission of dioxin or ozone-depleting chemicals. Inaddition, if discarded into the earth, they do not persist in theenvironment as containers or objects as foreign materials which mustbiodegrade (often over a number of years or decades) before they becomeenvironmentally innocuous. Instead, the waste hydraulically settablecontainer is essentially composed of the same materials already found inthe earth. Under the weight and pressure of typical landfills, such cupsand containers will crumble and break down into an environmentallyneutral granular powder that is compatible with the dirt and rockalready found in the landfill. If such containers are discarded onto theground, they will quickly decompose into an essentially dirt-likegranular powder when exposed to water or other forces of nature.

Furthermore, the hydraulically settable cups and containers are fullyrecyclable with a minimum amount of energy and effort. Unlike paper orplastic products, which require a substantial amount of processing inorder to restore them to a suitable state as raw starting materials,hydraulically settable containers can be ground-up and recycled bymerely reincorporating the grindings into new containers or othercementitious materials as an aggregate component within a virginhydraulic paste.

Tylose® and some of the other rheology-modifying agents help to increasethe yield stress, and hence the workability, of the hydraulicallysettable mixture. Tylose® has also been shown to increase theflexibility and tensile strength (if added in large enough amounts) ofthe final hardened container. Lower molecular weight rheology-modifyingagents can lubricate the aggregate and binder particles, as well as theadjacent mold surfaces, thereby increasing the moldability of themixture.

This quality of containing both a hydraulic binder and an aggregate is afurther departure from prior art containers, which are typicallycomprised of a uniform material such as polystyrene, paper, or metal,wherein impurities will impede their ability to be recycled. Incontrast, impurities such as napkins, straw papers, or food residues(which are all basically cellulose sources) do not impede the fullrecyclability of the hydraulically settable food and beverage containersof the present invention.

B. The Processing Techniques and Conditions

For purposes of simplicity, the term "molding," as used in thisspecification and the appended claims, is intended include the varietyof molding, casting, and extrusion processes discussed herein or thatare well known in the art with respect to materials such as clays,ceramics, and plastics, as well as the process of releasing (or"demolding") the hydraulically settable product from the mold. The term"molding" also includes the additional processes that might occur whilethe hydraulically settable mixture is in the mold, e.g., heating thehydraulically settable mixture, the reaction of the hydraulic mixturewith aluminum or other metals release gas bubbles which are incorporatedwith the hydraulically settable mixture, and the expansion of the volumeof the hydraulically settable mixture in the mold.

In order for the hydraulically settable mixtures of The presentinvention to be effectively molded, it is important that thehydraulically settable composition be form stable in the green state;that is to say, the molded product must rapidly be able to support itsown weight. Further, it must harden sufficiently that it can be quicklyejected from the mold. Otherwise, the cost of molding may make theprocess uneconomical.

The molding operation during which form stability achieved needs tooccur in less than one minute for a typical product to be economicallymass producible. Preferably, such form stability will occur in less than10 seconds, and most preferably in less than 1-3 seconds.

In addition, the surface of the molded cementitious article cannot betoo sticky, as that would make the demolding process impossible and makeit difficult to handle and stack the molded articles.

The combination of hydraulic binders, aggregates, fibers, and(optionally) air voids results in a composition that can be formed intorelatively thin sheets having roughly the same thickness as conventionalcups and containers made from paper or polystyrene. The compositions canreadily be molded or processed into a variety of shapes, including cups,containers, plates, platters, trays, "clam-shell" cartons, boxes,straws, lids, utensils, and similar products.

The resulting hydraulically settable containers also have low bulkdensity (often the bulk specific gravity is less than about 1 g/cc),resulting in a lightweight product which is comparable to conventionaldisposable cups and containers made of polystyrene and paper.

In order for the material to exhibit the best properties of high tensilestrength, toughness, and insulation, the fibers can be unidirectionallyor bidirectionally aligned or stacked according to the presentinvention, instead of being randomly dispersed, throughout thestructural matrix. It is often preferable for the fibers to be laid outin a plane that is parallel to either of the two surfaces of thehydraulically settable sheet or container wall.

Such alignment of fibers can be achieved by any number of moldingtechniques, such as by jiggering, ram-pressing, pull-trusion, hotpressing, extrusion, or calendering the hydraulically sortable mixture.Generally, the fibers are oriented in the direction of the flow ofmaterial during the molding process. By controlling the flow patterns ofthe material during the molding process, it is possible to build acontainer having the desired fiber orientation.

These processes also result in near zero porosity in terms of relativelylarge, continuous and unwanted air pockets which usually occur duringnormal concrete manufacture. This greatly increases the compressive andtensile strengths of the hydraulically settable material and reduces thetendency of the matrix to split or tear when the container is exposed toexternal mechanical forces.

The undesirable discontinuities and voids in typical cementitiousproducts should not be confused with the finely dispersed micro-pocketsof air (or other gas) that may be intentionally introduced into thehydraulically settable structural matrix by the direct introduction ofgas, the use of a high shear mixer, or the addition of reactive metals.Undesired voids or discontinuities are large and randomly dispersed, andoffer little in terms of added insulative properties, while at the sametime greatly reducing the integrity of the structural matrix andreducing its strength characteristics.

In contrast, the intentionally introduced gas bubbles or voids aregenerally uniformly and finely dispersed throughout the hydraulicallysettable mixture and are able insulate while allowing sufficientstrength of the material for use in making food or beverage containers.

It is generally possible to obtain acceptable levels insulation whileincreasing the strength of the container using lightweight aggregateswhich contain air voids. This allows for a stronger, more continuoushydraulically settable binder matrix holding the particles together.

Those cups and other containers incorporating a significant amount offinely dispersed gas bubbles or voids exhibit insulating propertiessimilar to those of polystyrene cups and containers, and yet havesufficient compressive, tensile, and flexural strengths that they willnot break when dropped onto a marble surface from heights as high as twoor more meters. This would not be expected, since concrete in thincross-sections is usually very weak and brittle with extremely lowflexural strength and elasticity.

Hydraulically settable containers made according to the presentinvention have been shown to provide sufficient insulation for hotdrinks (at least about 45° C., preferably at least about 65° C., andmost preferably at least about 80° C.) and food products (at least about25° C.) over the time period typically used in the dispensing of suchfood and beverages the fast food industry. In addition, the materialshave demonstrated the ability to keep foods (including even ice cream orother frozen products) and beverages cold (below about 15° C. and evenbelow about 0° C. for some food products) for the time necessary forconsumption.

By altering the quantities of cement, water, aggregates, fibers, andrheology-modifying plasticizing agents, is possible to control therheology, or flow property, of the hydraulic paste. For example, whenram-pressing, jiggering or injection molding is used, it may often bepreferable to start with a relatively highly viscous hydraulicallysettable mixture which will be highly form stable in the green state;the resulting molded product will then maintain its shape after beingformed, even before being dried or hardened.

When extrusion, calendering, pull-trusion, or hot pressing is used, thehydraulically settable mixture is preferably less viscous and has alower yield stress so that it will be more workable and flow easier.Because containers formed by these methods will usually be heated duringformation in order to remove much of the water in order achieve a drier,more form stable product, it will not be necessary for the hydraulicallysettable mixture to have as high a yield stress or initial formstability as in other molding processes.

Nevertheless, even these less viscous hydraulically settable mixturesare able to achieve rapid form stability when heated, making themanufacturing processes using them commercially acceptable and capableof mass producing the products. This is important because the longer theproduct remains in the mold, the higher the cost of manufacturing mostcases.

Whether a more or less viscous hydraulic paste required, it is generallydesirable to include as little water as is necessary to impart therequisite rheology for a particular molding process. One reason forminimizing the water is to control the capillary action of the water inhydraulically settable mixture, as this may cause stickiness of thehydraulically settable mixture, which in turn can cause problems indemolding the mixture from the mold. Minimizing the amount of watereliminates the free water and reduces the chemical and mechanicaladherence of the material to the mold. Hence, the capillary action andrelated surface tension of the water should be minimized, if possible,in order for there to be quick release of the hydraulically settablemixture during the molding process.

Furthermore, the resulting hydraulically settable products are strongerif less water is used. Of course adding more water initially willrequire that more water be removed from the hydraulic mixture during thedrying hardening process, thereby increasing manufacturing costs.

In order to obtain a hydraulically settable mixture having theappropriate properties of workability and green strength, it isimportant to adjust the water content combination with the use of arheology-modifying agent and, optionally, a dispersant within thehydraulically settable mixture. As discussed above, there are a varietyof suitable rheology-modifying agents.

The rheology-modifying agent increases the yield stress and makes themixture more plastic, so that it can be deformed and molded and thenmaintain its shape upon release of one molding pressure. This allows themolded product to withstand forces such as gravitational forces (thatis, it can support its own weight without external support) as well asforces involved in demolding the product and subsequent handling thecontainer before it has become substantially hardened.

There are several modifications to conventional molding processes whichare preferably employed in order to ease the manufacturing process. Forexample, it is frequently desirable to treat the mold with a releasingagent in order to prevent sticking. Suitable releasing agents includesilicon oil, Teflon®, Deleron®, and UHW®. Preferably, the mold itselfwill be made of stainless steel and/or coated with a material having avery slick finish, such as Teflon®, Deleron®, or chrome plating polishedto about 0.1 RMS.

The same effect can be achieved from the use frictional forces. Byspinning the head of the molding apparatus against the interior and/orexterior surfaces of the cementitious material, any chemical andmechanical adherence (i.e., stickiness) to the mold can be overcome.

During the process of molding and/or curing the cemenitious mixture, itis often desirable to heat up the cementitious mixture in order tocontrol the air void system allowing for proper control of the porosityand the volume the container. However, this heating process also aidsmaking the cementitious mixture form stable in the green state(immediately after molding) by allowing the surface to gain strengthquickly. Of course, this heating aids in rapidly removing significantamounts of the water from the cementitious mixture. The result of theseadvantages is that the use of the heating process can ease themanufacturing of the cementitious food and beverage containers.

If a gas has been incorporated into the cementitious mixture, heatingthat mixture to 250° C. will result (according to the gas-volumeequation) in the gas increasing its by about 85%. When heating isappropriate, it has been found desirable for that heating to be in therange from about 100° C. to about 250° C. More importantly, whenproperly controlled, heating will not result in the formation of crackswithin the structural matrix of the container or imperfections in thesurface texture of the container.

In fact, the process of adding CO₂ gas to the cementitious mixtureduring the molding process can help the molded product to quickly gainstability. For the foregoing disclosure, it will be apparent that thiscan be accomplished by the addition of a CO₂ gas or CO₂ generatingmaterial, such as an easily oxidized metal like zinc or aluminum,wherein the CO₂ generating process can be accelerated by the addition ofa base and/or heat.

The Mixing Process

While a variety of possible molding approaches can be used in themanufacturing of the containers of the present invention, as discussedabove, there are currently three preferable methods: "direct molding,""wet sheet molding," and "dry sheet molding." While the composition ofthe hydraulically settable mixture will vary in the different moldingprocesses, the mixing process will be substantially the same. Of course,different equipment will be used to conveniently provide feed stock tothe molding equipment.

In order to prepare a desired hydraulically settable mixture, the fiber,water, rheology-modifying agent, and other additives are preferablyblended together in a high shear mixer in order to form awell-dispersed, homogeneous mixture. High shear mixing is used for theaddition of fibrous material to insure that the fibers are welldispersed throughout the mixture. This results in a more uniformlyblended mixture, which improves the consistency of the green mixture andincreases the strength of the final hardened product. It may also bepreferable to add the hydraulic binder, as well as certain lowerconcentration aggregates such as mica, during the high shear mixing stepin order to obtain a homogenous mixture in the shortest possible time.

The addition of fibrous materials by normal cement mixing techniquesusually results in the conglomeration of the fibers, leading todeformities in the resulting sheets or articles. Standard mixers, suchas drum mixers, combine the components of the desired mixture byapplying low energy stirring or rotating to the components. In contrast,high shear mixers are capable of rapidly blending the mixture so as toapply high shearing forces on the particles within the hydraulicallysettable materials and the added fibrous materials.

As a result, the fibers and particles are uniformly dispersed throughoutthe mixture, thereby creating a more homogenous structural matrix withinthe hardened sheets. Fine particulate aggregates of relative highstrength (such as sand, silica, or alumina) can also be blended using ahigh speed mixer, although not if included in such high concentrationsto cause the hydraulic mixture to have a relatively low water contentand high viscosity.

Thereafter, aggregates included in higher concentrations (and sometimesthe hydraulic binder) are blended into the mixture using a low shearmixer. This is particularly true where lightweight aggregates are addedwhich cannot withstand high shear conditions without breaking, such asperlite or hollow glass spheres. It is preferable that the size of theaggregates not exceed about 30% of the final thickness of the sheet,since oversized aggregates could damage the rollers and create flawswithin the sheet surface.

Whether or not the hydraulic binder is added during the steps of high orlow shear mixing depends on the nature of The hydraulic binder, as wellas how the mixture is handled. It is believed that high shear mixing ofthe hydraulic cement after the formation of a particulate hydrosol gelcan disrupt the gel and result in a final hardened product havingdramatically lower compressive and tensile strengths.

In alternative embodiments, other additives, such as air-entrainingagents and reactive metals, can be incorporated into the mixture inorder to obtain a final material with lower density and higherinsulating ability.

In a typical mixing process in the laboratory, the appropriatecomponents are blended using a high shear, high speed mixer for about 1minute. Thereafter, the remaining components are blended into themixture using a low shear, low speed mixer for about 5 minutes. Thetotal mixing time per batch of material is therefore about 6 minutes,although this may be varied depending upon the nature of thehydraulically settable mixture. Industrially, this mixing process can besubstantially shortened by the use of appropriate mixers; specifically,the currently preferred method of mixing being a continuous mixingsystem.

In one embodiment, a cement mixer capable of both high and low shearmixing is used to meter and mix the materials in a batch mode. Thismixer can handle up to 350 l of material per batch and, assuming a 6minute mix cycle, is capable of producing 2,000 kg of a hydraulicallysettable mixture per hour, assuming 0.5 g/cm³ per cubic foot.

In an alternative embodiment, high speed, high shear mixers described inU.S. Pat. No. 4,225,247 entitled "Mixing and Agitating Device" and U.S.Pat. No. 4,552,463 entitled "Methods and Apparatus for Producing aColloidal Mixture" can be used for mixing the hydraulically settablemixture. Thereafter, the mixture can be transferred to a low speed, lowshear mixer in order to complete the mixing process. The mixing step mayalso be combined with the extrusion step (discussed below) using modernextrusion equipment that includes a high shear mixing chamber.

The currently preferred embodiment for the industrial setting isequipment in which the materials incorporated into the hydraulicallysettable mixture are automatically and continuously metered, mixed,deaired, and extruded by a twin auger extruder apparatus. A twin augerextruder apparatus has sections with specific purposes such as low shearmixing, high shear mixing, vacuuming, and pumping. A twin auger extruderapparatus has different flight pitches and orientations which permitsthe sections to accomplish their specific purposes.

It is also possible to premix some of the components in a vessel, asneeded, and pump the premixed components into the twin auger extruderapparatus. The preferable twin auger extruder apparatus utilizes uniformrotational augers wherein the augers rotate in the same direction.Counter-rotational twin auger extruders, wherein the augers rotate inopposite directions, accomplish the same purposes. A pugmill may also beutilized for the same purposes. Equipment meeting these specificationsare available from Buhler-Miag, Inc., located in Minneapolis, Minn.

The internal components of the mixer can be made of stainless steelbecause the abrasion to the mixer is not great due to the relativelyhigh water content. However, the mixer components can be carbide coatedfor extended life, thereby resisting any abrasion and the strongly basicconditions expected from a mixture containing aggregates and a hydraulicbinder.

The various component materials that will be combined within thehydraulically settable mixtures of the present invention are readilyavailable and may be purchased inexpensively in bulk quantities. Theymay be shipped and stored in bags, bins, or train cars, and later movedor unloaded using conventional means known in the art. In addition, thematerials can be stored in large storage silos and then withdrawn andtransported by means of conveyors to the mixing site.

As previously discussed, the hydraulically settable mixture ismicrostructurally engineered to have certain desired properties.Consequently, it is important to accurately meter the amount of materialthat is added during any batch or continuous mixing of the components.

The "Direct Molding" Process (a) Positioning

After the hydraulically settable mixture has been prepared as discussedabove, the next step in the "direct molding" process is positioning thecementitious mixture between a set of dies for subsequent shaping of thecementitious container. The dies comprise a male die having a desiredshape and a female die having a shape substantially complementary tothat of the male die. Accordingly, as the cementitious mixture ispressed between the dies, the cementitious mixture is formed into acontainer having the complementary shape of the dies.

The present invention envisions two general methods for positioning thecementitious mixture between the male die and the female die. In thepreferred embodiment, the male die is partially inserted into the femaledie such that a gap distance is created between the dies. The "gapdistance" is defined as the distance one die must travel with respect tothe other die for mating of the dies. The dies are "mated" when they areinserted into one another so as to form a mold area between the dies.The "mold area" defines the desired shape of the container and is thearea that the cementitious mixture is pushed into when the dies aremated.

When the dies are positioned so as to have a gap distance, a cavityremains between the dies. This "cavity" comprises the mold area betweenthe dies, and a second area also between the dies which corresponds tothe gap distance. Once the cavity is formed, the cementitious mixturecan be positioned into the cavity, and thus between the dies, by beinginjected through a hole in one of the dies or through he gap distance.

In the preferred embodiment, the female die is positioned verticallyabove the male die. The cementitious mixture is then injected betweenthe dies through an injection port extending through the female die. Thearrangement of having the female die above the male die is preferred,since after the forming of the cementitious container, the dies areseparated, and the force of gravity assists in insuring that thecementitious container remains on the male die. This is beneficial as itis easier to subsequently remove the container from the male die withoutdeforming the container.

Before positioning the cementitious mixture, it is preferable tominimize the gap distance between the dies so as to limit the movementof the cementitious mixture during the final pressing or mating of thedies. Minimizing the movement of the mixture decreases the chance ofirregularities in the final container as a result of differential flowin the cementitious mixture.

The gap distance between the male die and the female die is typically ina range of about 2 mm to about 5.0 cm, with 2 mm to about 3 cm beingpreferred, and 2 mm to about 1 cm being most preferred. It should benoted, however, that for unusually large objects, the gap distance maybe much larger to facilitate positioning of the cementitious mixture.

In an alternative embodiment, a vacuum auger is used to inject or feedthe cementitious mixture between the dies. The vacuum auger applies anegative pressure to the cementitious mixture as the mixture is beingtransferred for positioning. This negative pressure removes air trappedin the cementitious mixture. Failure to remove such air (unless the airis desired to create voids to impart insulative characteristics) canresult in the container having a defective or nonhomogeneous structurematrix.

The second method for positioning the cementitious mixture between thedies is performed while the dies are still fully separated. This methodcomprises forming a portion of the cementitious material into a mass,the portion being sufficient to create the container, then placing themass between the dies, typically by resting the mass on the top of themale die. Subsequently, as the dies are mated, the mass is pressedbetween the dies.

In an alternative embodiment, a template is used to position thecementitious mass. In this embodiment, the male die has a base with acircumference, and the template has a passage with a perimetersubstantially complimentary to the circumference of the base of the maledie.

This method comprises forming a portion of the cementitious mixture intoa mass having a diameter sufficiently large to span the passage of thetemplate. The mass is then placed on the template so as to span thepassage. Finally, the template is placed between the male die and thefemale die such that the passage is complementarily aligned with thedies. Thereby, as the dies are pressed together, the male die travelsthrough the passage of the template in order to press the cementitiousmixture between the dies.

The above method can further include the stem of depositing the templateonto the male die, such that the template becomes positioned about thebase of the male dies while the mass independently rests on the maledie. Subsequently, as the dies are pressed together, the mass is againpressed between the dies. Additional benefits relating to the use of thetemplate will be discussed hereinafter with respect to the step relatingto removing the container from the dies.

(b) Forming and Molding

The next step in the manufacturing process is pressing the cementitiousmixture between the male die and the female die in order to mold thecementitious mixture into the desired shape of the cementitiouscontainer.

The pressure exerted by the dies forms the cementitious mixture into thedesired configuration for the container. Accordingly, the pressure mustbe sufficient to actually mold the cementitious mixture between thedies. Furthermore, it is preferable that the pressure be sufficient toproduce a container with a uniform and smooth finished surface.

The amount of pressure applied to the cementitious mixture also affectsthe strength of the resulting container. Research has found that thestrength of the resultant product is increased for mixtures where thecement particles are close together. The greater the pressure used topress the cement mixture between the dies, the closer together thecement particles are pushed, thereby increasing the strength off theresulting container. That is to say, the less porosity that there is inthe cementitious mixture, the higher the strength of the resultingproduct.

As high pressures are applied to cementitious mixtures with lowconcentration of water, the space between the particles is decreased.Thus, the water existing within the mixture becomes more effective inencasing the particles and reducing their friction force. In essence, aspressure is applied to a cementitious mixture, the mixture becomes morefluid or workable and, thus, less water needs to be added. In turn, thestrength of the resulting product is increased. In application to thepresent invention, the higher the pressure exerted by the dies, thelower the amount of water that needs to be added to the mixture.

Although a high pressure is generally desirable, it can also have anegative effect. To produce a lightweight cementitious container, lowdensity aggregates (such as perlite hollow glass spheres) are typicallyadded to the mixture. As the pressure exerted by the dies is increased,these aggregates may be crushed, thereby increasing the density of theaggregate and the resulting container, thereby decreasing the insulativeeffect of the aggregates.

Accordingly, the pressure applied by the dies should be optimized so asto maximize the strength, structural integrity, and low density of thecementitious container. Within the present invention, the pressureexerted by the male die and the female die on the cementitious mixturepreferably within a range from about 50 psi to about 20,000 psi, morepreferably from about 100 psi to about 10,000 psi, and most preferablyfrom about 150 psi to about 2000 psi. However, as discussed below, theamount of pressure will vary depending upon the temperature and time ofthe molding process.

The step of pressing further includes expelling the air from between thedies when the dies are pressed together. Failure to remove such air canresult in air pockets or deformities in the structural matrix of thecementitious container. Typically, air between the dies is expelledthrough the gap distance between the dies as the dies are pressedtogether.

In an alternative embodiment, the dies may have a plurality of ventholes extending through the dies so as make them permeable. Accordingly,as the dies are pressed together, the air between the dies is expelledthrough the vent holes. The vent holes thus prevent air pockets whichcould deform the cementitious container from forming within the cavity.

The vent holes also prevent the creation of a vacuum within the cavityas the dies are separated, by allowing air to return into cavity. Such avacuum could exert an undue force on the newly formed cementitiouscontainer, thereby disrupting its structural integrity. Furthermore,vent holes permit the escape of excess steam created during the heatingprocess which will be discussed later. The vent holes can exist ineither or both of the dies.

(c) Heating

The next step in the manufacturing process is heating the cementitiousmixture for a sufficient period of time to impart improved formstability to the cementitious container. The preferred method forheating the cementitious mixture comprises heating the male die and thefemale die each to a respective temperature before pressing thecementitious mixture.

Increasing the temperature of the dies prior to the pressing step servesseveral functions. For ease in molding the cementitious mixture into acontainer without crushing the aggregate, an excess of water is added tothe mixture. By applying heated dies to the mixture, a portion of thewater in the cementitious mixture evaporates in the form of steam,thereby decreasing the volume percent of water and, thus, increasing theultimate strength of the container.

Furthermore, as the water on the surface of the container evaporates,that portion of the cementitious mixture rapidly becomes dry. Thefriction forces between the dry particles in the cementitious mixtureform a strong thin "shell" around the container which provides thecementitious container with form stability.

The application of heat to the cementitious mixture also increases therate of curing. As discussed below, however, the dies remain pressed onthe cementitious mixture for such a short period of time that only afraction of the cementitious mixture reacts to become cured. Asubstantial amount of strength required for form stability is thus aresult of the friction forces between the dry particles. As a result,the container is still in the green state even after achieving formstability.

The ability to rapidly impart form stability to the cementitiouscontainer in the green state is important, as permits mass production ofthe containers. Form stability allows the containers to be quicklyremoved from the pressing apparatus so that new containers can be formedusing the same pressing or molding equipment.

Another purpose for increasing the temperature of the dies is tominimize adherence of the cementitious mixture the dies. As the steam isemitted from the cementitious mixture, it creates a "cushion" betweenthe dies and the cementitious mixture. This steam boundary layerprovides a substantially uniform force that pushes the cementitiousmixture away from the die and, thus, prevents the cementitious mixturefrom sticking to the dies.

Furthermore, experiments have determined that if the male die and femaledie have a variance in temperature, the cementitious material will havea tendency to remain on the die with the lower temperature when the diesare separated. Accordingly, one can select the die on which thecementitious container is to remain on as the dies are separated, byhaving the desired die at a lower temperature.

The respective temperatures of the dies are important for maximizing thespeed of the manufacturing process and are dependent, in part, upon theduration that the dies are in contact with cementitious material. Ingeneral, it is desirable that the temperature be as high aspossible--the higher the temperature, the faster the drying on thesurface of the cups, the quicker the cups can be removed, and the morecups that can be made per unit time.

The problem with higher temperatures, however, is that if thecementitious mixture becomes too hot, the water throughout thecementitious mixture, as opposed to just on the surface of thecontainers, turns to steam. The sudden release in pressure associatedwith demolding can result in the cracking, or even explosion, of themolded container once the dies are separated. However, this cracking canoften be solved by faster closing and opening speeds of the press.

Moreover, the faster the cementitious material cures, the greater thelikelihood of a deformity forming within the cementitious container as aresult of differential flow. That is, as the dies are pressed together,the cementitious material flows into the desired shape. However, oncethe cementitious mixture on the surface of a container starts dry, thedrier cement has different flow properties than the remaining wetcementitious material. This differential flow properties can result indeformities such as agglomerates, voids, cracks, and otherirregularities in the structural matrix of the cementitious container.

Accordingly, the interrelationship between time and temperature is thatthe temperature of the dies can be increased as the time that the diesare in contact with the cementitious mixture is decreased. Furthermore,the temperature can be increased as the gap distance between the diesdecreased. However, there are limits to how high the temperature can gobefore the hydraulic mixtures become damaged.

To achieve the above desired objectives, it is preferable to heat thefemale and male die to a temperature within the range from between about50° C. to about 250° C., more preferably to between about 75° C. toabout 160° C., and most preferably to between about 120° C. to about140° C. For reasons previously discussed, it is desirable to have thecementitious container remain on the male die after separation of thedies. Accordingly, the male die preferably has a lower temperature thanthe female die. The temperature variance between the female die and maledie should preferably be in the range from about 10° C. to about 30° C.

The duration in which the heated male die and the heated female die areboth in contact with the cementitious material (i.e., the time that thedies are mated) is preferably within the range from about 0.05 secondsto about seconds, more preferably between about 0.7 seconds to aboutseconds, and most preferably between about 0.8 seconds about 5 seconds.

In an alternative embodiment, the step of heating the cementitiouscontainer further includes exposing the cementitious container to heatedair after the dies are separated but before the container is removedfrom the die, that is while the cementitious container is supported onthe male die. Exposure to heated air insures that the container is formstable before it is removed from the die.

In another alternative embodiment, the step of heating the cementitiousmixture can be accomplished by exposing the cementitious mixture tomicrowaves.

(d) Removing

After the molded article has achieved some form stability, the newlyformed cementitious container is removed from the dies. In the preferredembodiment, the newly formed cementitious container remains on the maledie when the dies are separated. In one embodiment, the male die and thefemale die are rotated as they are separated so as to prevent thecementitious container from adhering to the dies.

As previously discussed, once the dies are separated, heated air can beblown over the container for a few seconds to further increase formstability. The cementitious container can then be removed from the maledie without deformation. In the preferred embodiment, a standard processknown as airveying is used to remove the cementitious container from themale die. Airveying is a process in which a negative pressure is appliedto the container for sucking the container from off the die. Thecontainer then travels through a "U" shaped tube that deposits thecontainer right side up.

The airveying process is preferable due to its gentle handling of theform stable containers and its low operating and capital costs. Heatingair which is present to dry containers may be used to provide the bulkair transport carrying the containers through the length of the tubes.The air ducts are simply ports in the male die through which air can beinjected to provide a uniform force to push the container off the maledie. Such air ducts have substantially the same size, shape, andposition as the vent holes previously discussed.

In one embodiment, the air ducts and vent holes may be one and the same.The air inserted in the air ducts must be low enough not to damage thecontainers. It is envisioned in the preferred embodiment that air ductsare located on the male die to help eject the containers from the maledie into the tubes.

In an alternative embodiment, the cementitious container can bemechanically removed from the male die by simply picking up thecontainer. Such a process, however, requires exceptional care so as notto deform the container. The preferred method for mechanically removingthe cementitious container incorporates using a template.

The template is circumferentially located at the base of the male dieand is removable. The cementitious container is loaded onto the templatevia the lip of the cementitious container by either lifting the templateor lowering the male die. When the container is removed from the dies,the container is form stable due to its dried surface. However, thecontainer will still have green cement between its walls and, thus, itwill not have reached its maximum strength. In such a condition, thecementitious container is strongest in compression along its verticalaxis. Accordingly, the benefit of using the template is that the forceapplied for removing the container is applied along the strongest axisof the container, thereby minimizing possible deformation to thecontainer.

(e) Initial Hardening

Once molded, the cementitious mixture is allowed to harden in thedesired shape of the cementitious container. To economically produce theinventive container, it must be rapidly hardened to a point where it hassufficient strength to be packaged, shipped, and used withoutsubstantial deformation.

Hardening of the container is accomplished by exposing the container toheated air, such as in a conventional tunnel oven. The application ofthe heated air drives off a portion of the water in the cementitiousmixture, thereby increasing the friction forces between the particlesand, thus, increasing the strength of the resulting container.Furthermore, the application of heated air to the containers increasesthe reaction rate of the cement, which provides early strength to thecontainer through curing. Accordingly, hardening results from both anincrease in the friction forces between the particles and curing of thecementitious mixture.

In the preferred embodiment, the container is hardened only to theextent that it has sufficient strength for packaging and transportwithout deformation. Ideally, the hardened container retains a smallamount of unreacted water that permits the container to continue tocure, and thus increase in strength, during the period of time it istransported and stored prior to use.

In yet another embodiment, the air is blown over the container toincrease the rate at which the cementitious mixture dries, therebyincreasing the rate of hardening.

The air can also be applied through an autoclave capable of regulatingthe humidity, pressure, and temperature in the environment in which thecontainer is cured, Increasing the humidity and temperature assists inproducing more complete hydration of the cementitious mixture, therebyproducing a stronger container.

It is this ability to rapidly harden the cementitious containers thatmakes it possible to economically complete the mass production of thecementitious containers.

In summary, the following conclusions can be drawn with respect to thedrying of the cementitious product:

(1) The higher the temperature, the shorter the drying time.

(2) The higher the air speed, the shorter the drying time.

(3) Once a majority of the water is removed from a container, exposingthe container to temperatures above 250° C. will burn organic fibers inthe mixture, thereby decreasing tensile strength of the fibers andcontainers.

(4) The thinner the material wall of the container, the shorter thedrying time.

(5) The higher the temperature is above 100° C., the lower the tensilestrength of the resultant container.

3. The "Wet Sheet Molding" Process (a) Extrusion.

Once the hydraulically settable mixture has been properly blended, it isextruded through a thick sheet-type die. The hydraulically settablemixture is formed into sheets of precise thickness by first extrudingthe material through an appropriate extruder die and then passing theextruded material through one or more pairs of reduction rollers.

Within the interior chamber, one or more auger screws exert forwardpressure on the hydraulically settable mixture and advance it throughthe interior chamber toward a die head having a transverse slit. Thecross-sectional shape of the die slit is configured to create a sheet ofa desired width and thickness generally corresponding to die width andthickness.

Alternatively, the extruder apparatus may comprise piston instead of anauger screw in order to exert forward pressure on the hydraulicallysettable mixture and advance it through the interior chamber. Anadvantage of using a piston extruder is the ability to exert muchgreater pressures upon the hydraulically settable mixture. Nevertheless,due to the highly plastic-like nature of mixtures typically employed thepresent invention, it not generally necessary, or even advantageous, toexert pressures greater than those achieved using an auger-typeextruder.

In contrast, an important advantage of using an auger type extruder isthat it has the ability to remove unwanted macroscopic air voids withinthe hydraulically settable mixture. Failure to remove unwanted air voidscan result in the sheet having a defective or nonhomogeneous structuralmatrix. Removal of the air voids may be accomplished using conventionalventing means known in the extrusion art, wherein the mixture is firstpassed into a vacuum chamber by a first auger screw and then extrudedthrough the extruder die head by means of a second auger screw.

Alternatively, the unwanted air voids may be removed from thehydraulically settable mixture by a process known as "venting", whereinthe excess air collects under pressure within the interior chamber andescapes from the extruder chamber while the mixture is compressed andmoved forward by the auger screw.

Although the preferred width and thickness of the die will depend uponthe width and thickness of the particular sheet to be manufactured, thethickness of the extruded sheet will usually be at least twice, andsometime many times, the thickness of the final calendered sheet. Theamount of reduction (and, correspondingly, the thickness multiplier)will depend upon the properties of the sheet in question. Because thereduction process helps control fiber orientation, the amount ofreduction will often correspond to the degree of desired orientation.

In addition, the greater the thickness reduction, the greater theelongation of the sheet. In a typical manufacturing process an extrudedsheet with a thickness of about 6 mm is calendered to form a wet sheetwith a thickness of about 0.5 mm to about 1 mm.

Although the die slit is generally rectangularly shaped, it may containareas of increased thickness along its width in order to form anextruded sheet having varying thickness along its width. In this case,it will also generally be preferable to pass the sheet through a seriesof rollers having recesses or gap variations which correspond to theareas of increased extruded thickness. In this way a sheet havingreinforced areas of increased strength and stiffness can be produced.

In addition to narrow die slits to form flat sheets, other dies may beused to form other objects or shapes, the only criterion being that theextruded shape be capable of being passed between a pair of rollers. Forexample, it may not be desirable to extrude an extremely wide sheet,which would require a very large, expensive die. Instead, a pipe may beextruded and continuously cut and unfolded using knife located justoutside the die head.

It will be understood that an important factor which will affect theoptimum speed or rate of extrusion is the final thickness of the sheet.A thicker sheet contains more material and will require a higher rate ofextrusion provide the necessary material. Conversely, a thinner sheetcontains less material and will require a lower rate extrusion in orderto provide the necessary material.

As set forth above, adequate pressure is necessary in order totemporarily increase the workability of the hydraulically settablemixture in the case where the mixture has deficiency of water and has adegree of particle packing optimization. In a mixture that is waterdeficient, the spaces (or interstices) between the particles containinsufficient water to lubricate the particles in order to createadequate workability under ordinary conditions.

However, as the mixture is compressed within the extruder, thecompressive forces force the particles together, thereby reducing theinterstitial space between the particles and increasing the apparentamount of water that is available to lubricate the particles. In thisway, workability is increased until the mixture has been extrudedthrough the die head, at which point the reduced pressure causes themixture to exhibit an almost immediate increase in stiffness and greenstrength, which is generally desirable.

It should be understood that the pressure exerted on the hydraulicallysettable mixture during the extrusion process should not be so great soas to crush or fracture the lightweight, lower strength aggregates (suchas perlite, hollow glass spheres, pumice, or exfoliated rock).

In light of each of the factors listed above, the amount of pressurewhich will be applied by the extruder in order to extrude thehydraulically settable mixture will preferably be within the range frombetween about 50 kPa to about 70 MPa, more preferably within the rangefrom between about 150 kPa to about 30 MPa, and most preferably withinthe range from between about 350 kPa to about 3.5 MPa.

In some cases, particularly where a lower density, higher insulatingsheet is desired, it may be advantageous employ a blowing agent, whichis added to the mixture prior the extrusion process.

It will be understood that the extrusion of hydraulically settablebinder through the die head will tend unidirectionally orient theindividual fibers within the hydraulically settable mixture along the"Y" axis, or in the lengthwise direction of the extruded sheet. As willbe seem herein below, the calendering process will further orient thefibers in the "Y" direction as the sheet is further elongated during thereduction process. In addition, by employing rollers having varying gapdistances in the "Z" direction (such as conical rollers) some of thefibers can also be oriented in the "X" direction, i.e., along the widthof the sheet. Thus, it is possible to create a sheet by extrusion,coupled with calendering, which will have bidirectionally orientedfibers.

(b) Forming and Molding

Once the sheet is formed, the next step is to fashion a portion of thesheet into the desired shape for the container or article. In thepreferred embodiment, the sheet pressed between a male die of a desiredshape and a female die having a substantially complementary shape to themale die. As a portion of the sheet is pressed between the dies, themixture is formed into a container having the complementary shape of thedies.

Although solid single piece dies (the male die and the female die eachcomprising one solid piece) are the preferred dies based on ease andeconomy, alternative dies include split: dies and progressive dies. Theuse of multi-component split dies permits the production of complexshapes that are easily removed from the mold.

In contrast to the split die, where the components press togethersimultaneously to form the object, a progressive die is amulti-component die whose various parts are pressed together in adelayed sequence to form the desired container. By selecting the orderand time when the various components of the die are pressed together, acomplex container can be formed having a more uniform thickness.

For example, a progressive male die used to make a bowl may include abase and a side component. By having the base component press first, theremainder of the sheet is pulled in against the side of the female die.The side component of the male die can then be pressed to form the sideof the bowl without stretching the sheet, thereby forming a bowl havinga more uniform thickness.

Just as in the direct molding process, the amount of pressure exerted bythe dies onto the sheet serves several functions which must beconsidered when determining how much pressure to apply. While a sheet ofmaterial is used as compared with directly injecting the material, theparameters and the cautions discussed above will generally apply to thewet sheet molding process.

In an alternative method for fashioning the container from the sheet,the various methods of vacuum forming, as commonly used in the plasticsindustry, can be incorporated Vacuum forming uses atmospheric pressure(about 14.7 psi) force the sheet to conform to a mold. Both male andfemale molds can be used for vacuum forming.

The term "vacuum mold" as used in the specification and appended claimsis intended to include either or both the male mold and female mold usedin vacuum forming.

Drape forming is used with male molds. The sheet ms positioned over thetop of the mold, or the mold is placed into the sheet. The air betweenthe sheet and the mold is then evacuated, contouring the sheet aroundthe mold. The resulting product is thickest in the center of the partwhere the material first touches the mold. It is thinnest in high drawareas around the periphery, which contacts the mold last.

Straight vacuum forming is used with female molds. The sheet is sealedagainst the top of the female mold. The mold cavity is evacuated, andatmospheric pressure pushes the material against the sidewalls of thecavity. This forming technique results in material distribution (thin inthe middle and thick around the edges) that is essentially opposite thatobtained when the same part is produced by drape forming on a male mold.

Drape vacuum forming, as opposed to drape forming, similar to straightvacuum forming except that the edges the sheet are pressed all the wayto the base of the female mold before the cavity is evacuated. Thisprovides a better vacuum for the molding process.

Snapback, billow/air slip, and billow drape are step vacuum formingtechniques designed to improve the wall thickness uniformity of productsproduced on male molds by prestretching the sheet prior to itscontacting the mold. Stretching the sheet freely in air without touchinganything allows the material to thin out uniformly. As a result, surfacearea of the sheet is also increased so that it more closely matches thatof the mold.

Snapback vacuum forming utilizes a vacuum box to prestretch the sheet.The vacuum box is mounted to a platen opposite the male mold. Thecementitious sheet is sealed against the vacuum box, and a partialvacuum, sufficient achieve the desired amount of stretching, is appliedto the box. The mold is then pushed into the concave sheet. The box isvented to the atmosphere and a vacuum is drawn on the mold Theatmospheric pressure then forces the material against the mold.

Billow/air-slip vacuum forming utilizes a pressure box with a male moldpositioned inside it. The sheet is sealed against the box. The box ispressured with compressed air and the sheet billows up to form a bubblethat provides the appropriate stretching. The mold is pushed up into theconvex bubble. The box and the male mold are then evacuated and thesheet is forced against the mold.

Billow drape vacuum forming is a reverse draw technique that utilizes apressure box to blow a bubble in the sheet. The male mold, mountedopposite the box, is pushed into the convex bubble. The air in thebubble is vented to the atmosphere in a controlled manner. By matchingthe amount of air being vented to that being displaced by the mold, thesheet material is wiped or draped against the mold. When the moldcompletely penetrates the sheet, a vacuum is applied to the mold and thebox is vented to the atmosphere to complete the forming operation.

Plug-assist and billow/plug-assist/snap back are multistep vacuumforming techniques designed to improve the wall thickness uniformity ofparts produced with female molds. They utilize mechanical assists (orplugs) to force more material into high dry areas of the part.

Plug assist vacuum forming is used in conjunction with straight vacuumor drape forming techniques. The plug is mounted on a platen oppositethe female mold. The sheet is sealed against the mold, and the plugpushes the material into the mold prior to drawing a vacuum. When themold is evacuated, the material is forced off the plug and up againstthe mold cavity.

Billow/plug-assist/snap back forming combines several different formingtechniques. The sheet is sealed against a female mold. The mold ispressurized to stretch the sheet by blowing a bubble. A plug mountedopposite the mold is forced into the convex bubble, and controlledventing of the displaced air in the bubble causes the material to bedraped over the plug. When the plug is fully extended, the mold isevacuated and the material is pushed off the plug and onto the mold.

Pressure forming uses compressed air in addition to atmosphericpressure, Pressures typically range from about 40 Pa to about 200 Pa.Pressure forming requires special equipment with platens and/or molds inpressure boxes capable of locking up and holding the necessary pressure,Pressure forming can be incorporated into any of the vacuum formingtechniques previously described,

The twin sheet forming process produces hollow parts. Two sheets arepositioned between two female molds with matching perimeters or contactsurfaces, The mold cavity contours may or may not be identical. Themolds come together and bind the two sheets together where the moldsmeet, The two sheets may be either pressure formed simultaneously vacuumformed subsequently utilizing conventional forming techniques.

The term "vacuum forming processes," as used in the appended claims, isintended to include pressure form and twin sheet forming processes inaddition to the specifically enumerated vacuum forming techniques.

(c) Heating and Form Stability

The creation of initial form stability in the hydraulically settableproduct after it is molded can be accomplished in substantially the sameway as with the direct molding process.

(c) Drying

Once initial form stability has been achieved, the hydraulicallysettable product can be dried and hardened by the same varioustechniques described above with respect to the direct molding process.

4. The "Dry Sheet Molding" Process (a) Extrusion.

The extrusion method used in connection with the "Dry Sheet Molding"process is, in all material aspects, substantially the same as thatpreferably utilized with the wet sheet molding process. Of course, theuse of different processing equipment down the processing line mayresult the need to make some modifications to the extrusion process, butsuch modifications are within the skill of the art light of theforegoing teachings.

(b) Calendering

In most embodiments of the dry sheet molding process, it will bepreferable to "calender" the extruded sheet passing it between at leastone pair of rollers, the purpose of which is to improve the uniformityand surface quality the sheet and also usually reduce the thickness ofthe sheet. In some embodiments, the calendering step will only reducethe thickness of the sheet by a small amount, if at all. In other cases,the calendering process will substantially reduce the thickness of thesheet.

As the thickness of the sheet is reduced when passing through a pair ofrollers, it will also elongate in the forward moving direction. Oneconsequence of sheet elongation is that the fibers will further beoriented or lined up in the "Y" direction. In this way, the reductionprocess in combination with the initial extrusion process will create asheet having substantially unidirectionally oriented fibers in "Y", orlengthwise, direction.

This process of squeezing or pressing the sheet, as well as the speeddifferential between the entering sheet and the rollers, creates acertain amount of shearing forces the sheet. The application of anexcessively large shearing force can disrupt the integrity of thestructural matrix of the sheet and create flaws within the sheet,thereby weakening the sheet. Because of this, the thickness of the sheetshould be reduced in steps small enough to prevent undo damage to thesheet. In most cases, the reduction of thickness of the sheet thougheach pair of rollers should be less than about 80% more preferably, thereduction should be less than about 50%.

The diameter of each of the rollers should be optimized depending on theproperties of the hydraulically settable mixture and the amount ofthickness reduction of the hydraulically settable sheets. Whenoptimizing the diameter of rollers, two competing interests should beconsidered. The first relates to the fact that smaller diameter rollerstend to impart a greater amount of shearing force into the sheet as itpasses between the rollers. This is because the rate reduction of thehydraulically settable sheet is much greater at any given speed with thesmaller diameter roller as it passes between the rollers.

Using larger diameter rollers allows more of the sheet to come incontact with the surface of the rollers as the sheet passes betweenthem. Thus, the step of squeezing or pressing the sheet into a thinnersheet by the rollers is accomplished along a shorter distance and in ashorter period of time when smaller diameter rollers are used ascompared larger diameter rollers.

However, the use of larger diameter rollers also has the drawback thatthe hydraulically settable material comes into contact with the rollerfor a greater period of time, thereby resulting in an increase in dryingof the sheet during the calendering process. While some drying isadvantageous, drying the sheet too quickly during the calenderingprocess could result in the introduction of fractures and other flawswithin the structural matrix. The use of smaller diameter rollersreduces the drying effect of the calendering process.

It is preferable to treat the roller surfaces in order to preventsticking or adhesion of the hydraulically settable sheet to the rollers.One method entails heating the rollers, which causes some of the waterwithin the hydraulic mixture to evaporate and to create a steam barrierbetween the sheet and the rollers. Evaporation of some of the water alsoreduces the amount of water within the hydraulic mixture, therebyincreasing the green strength of the sheet. The temperature of therollers, however, must not be so high as to dry or harden the surface ofthe sheet to the point which would create residual stresses, fractures,flaking, or other deformities or irregularities in the sheet.Accordingly, it is preferable to heat the rollers to a temperaturewithin the range from between about 50° C. to about 140° C., morepreferably no between about 70° C. to about 120° C., and most preferablyto between about 85° C. to about 105° C.

In addition, the rate of drying of the sheet can be reduced byincorporating aggregates having a low specific surface area. Aggregateswhich have a greater specific surface area can more readily release anywater absorbed within the aggregate as compared to aggregates having alower specific surface area.

Finally, it has been found that heating the hydraulically settablemixtures of the present invention increases the rate of the hydrationreaction between the hydraulic binder and water. Heating the hydraulicmixtures of the present invention makes it possible to obtainsubstantial hydration of the hydraulic binder in as little as one hour.Because a substantial amount of the final strength can be obtained evenbefore the hydration reaction has reached the standard 28-day level,heated hydraulically settable sheets of the present invention canachieve a substantial amount of their final strength within as little as10 minutes.

In an alternative embodiment, adhesion between the hydraulicallysettable sheets and rollers can be reduced by cooling the rollers to, orbelow, room temperature. Heating the mixture in the extruder to about85° C., for example, and then cooling the sheet surface causes thevaporizing water to condense, which is thought to create a thin film ofwater between the sheet and the roller. The rollers should be coolenough to prevent the surface of the sheet from adhering to the rollers,but not so cold that it causes the sheet to freeze or become so stiff orinflexible that it will fracture or shatter during the calenderingprocess.

Overcooling the material can also greatly retard the hydration reaction,although this may be desirable in some cases. Accordingly, it ispreferable to cool the rollers to a temperature within the range frombetween about 20° C. to about 40° C., more preferably to between about0° C to about 35° C., and most preferably to between about 5° C. toabout 3C° C.

Another way to reduce the level of adhesion between the rollers and thehydraulically settable sheet is to treat the roller surfaces in order tomake them less amenable to adhesion. Rollers are typically made frompolished stainless steel and coated with an antistick material such aspolished chrome, nickel, or teflon.

It has been discovered that the amount of shear and downward pressure ofthe rollers can be reduced, while still deriving the same amount ofsheet reduction, by employing a roller having a slightly conical shapein conjunction with a flat roller. However, the degree of gapdifferential in the "Z" direction as a result of the conical shapeshould be controlled to prevent spreading or widening of the sheet inthe "X" direction, unless such widening is desired. However, widening isnot usually desired because the widened portion is not usually of aconstant thickness and must typically be trimmed and discarded. By usingconical rollers, it is possible to obtain higher elongation and sheetreduction without applying more shear to the sheet.

Orienting the fibers maximizes the tensile strength imparting propertiesof the fibers in the direction of orientation. In addition, orientingthe fibers is particularly useful to reinforce a hinge or score withinthe sheet. Fibers which are greater in length than the width of the foldor bend can act as a bridge to connect the material on either side ofthe fold or bend even if the matrix is partially or even substantiallyfractured along the fold or bend. This bridging effect is enhanced ifthe fibers are generally aligned perpendicular to the fold or bend.

Finally, it should be understood that due to the plastic nature andrelatively high level of workability of the hydraulically settablemixture, the calendering process usually not result in much compressionof the sheet. In other words, the density of the sheet will remainsubstantially the same throughout the calendering process, although somecompaction would be expected, particularly where the sheet has beensignificantly dried while passing between other reduction rollers. Wherecompaction is desired, the sheet can be passed between a pair ofcompaction rollers following a drying step, as set forth more fullybelow.

One of ordinary skill in the art will appreciate that the extrusion stepneed not formerly employ the use of an "extruder" as the term is used inthe art. The purpose of the extrusion step is to provide a continuous,well-regulated supply of hydraulically settable material to the rollers.The extrusion step preferably orients the fibers in the direction of theflow of the material. This may be achieved by other mechanisms known tothose skilled in the art to effect the "extrusion" or flow of materialthrough an appropriate opening.

(c) Roller Drying

Although the calendering step often results in partial or evensubstantial drying of the hydraulically settable sheet, it will bepreferable to further dry the sheet in order to obtain a sheet with thedesired properties of tensile strength and toughness. This may beaccomplished in a number of ways, each of which involves heating thesheet in order to drive off the excess water. A preferred method ofdrying the sheet involves the use of large diameter, heated dryingrollers known in the art as "Yankee" rollers. The main concern is thatthe combined surface areas of the rollers be adequate to efficientlyeffectuate drying of the sheet.

In contrast to the reduction rollers, which are generally aligned inpairs, the drying rollers are individually aligned so that the sheetpasses over a maximum surface of each roller individually in sequence.In this way, the two sides of the hydraulically settable sheet arealternatively dried in steps. While the sheet passes between thereduction rollers during the calendering step in generally linear path,the sheet follows a generally sinusoidal path when wrapping around andthrough the rollers (e.g., "Yankee" rollers) during the drying step.

The side adjacent to the first drying roller is heated by the dryingroller while the other side is exposed to air. The heated sheet loseswater in the form of vapor, which can escape out the sides of the rolleror the surface of the sheet opposite the roller. The vapor also providesa nonstick barrier between the sheet and roller. The drying rollers mayhave tiny holes within the surface in order to allow some the watervapor to escape through the holes during the drying step.

As the sheet continues on its path it is rolled onto a second dryingroller where the other side comes into contact with the roller surfaceand is dried. This process may be continued for as many steps as neededin order to dry sheet in the desired amount. In some cases it may bepreferable to dry one side of the sheet more than the other.

The temperature of the drying rollers will depend on a number offactors, including the moisture content of the as it passes over aparticular roller. In any event, the temperature of the drying rollersshould be less than about 300° C. Although the internal temperature ofthe hydraulically settable material should not be heated above 250° C.in order to prevent the destruction of the organic constituents (such asrheology-modifying agent or fibers), rollers heated to above thistemperature may be used so long as there is adequate water within themixture to cool the material as the water vaporizes. Nevertheless, asthe amount of water decreases during the drying process, the temperatureof the rollers should be reduced to prevent overheating of the material.

In some cases, it may be preferable to use a drying tunnel or chamber inconjunction with the drying rollers. In order to obtain the full effectof heat convection drying, it is often preferable to circulate theheated air in order to speed up the drying process.

In some cases, the drying process set forth above will be the final stepbefore the sheet is either used to form a container or other object or,alternatively, rolled onto a spool or stacked as sheets until needed. Inother cases, particularly where a sheet with a smoother, more paper-likefinish is desired, this drying step will be followed by one or moreadditional steps set forth more fully below, including a compacting stepand/or a finishing step. In the case of compaction, it is generallypreferable to leave the sheets with some amount of moisture to preventfracturing of the matrix during the optional compaction step. Otherwise,if the drying step is not followed by a compaction step, it is generallydesired to substantially dry out the sheet in order to quickly maximizethe tensile strength and toughness of the sheet.

(d) Finishing

In many cases, it may be desirable to compact the hydraulically settablesheet in order to achieve the final thickness, tolerance, and surfacefinish. In addition, the compaction process can be used to removeunwanted voids within the structural matrix. The sheet is passed betweena pair of compaction rollers after being substantially dried during thedrying process. The compaction process generally yields a sheet withhigher density and strength, fewer surface defects, and a smallerthickness.

The compaction process preferably yields a sheet of reduced thicknessand increased density without causing further elongation of the sheetand without negatively disrupting or weakening the structural matrix. Inorder to achieve compaction without elongating the sheet and withoutweakening the structural matrix, it is important to control the dryingprocess so that the sheet contains an amount of water within an optimumrange. If the sheet contains too much water, the compaction rollers willelongate the sheet in similar fashion as the reduction rollers. In fact,the compaction rollers are substantially the same as the reductionrollers, the only difference being that compaction, rather thanelongation, will occur if the sheet is dry enough.

On the other hand, overdrying the sheet prior to the compaction step canyield a weaker sheet. At some point the hydraulically settable sheet canbecome so dry and hard that the structural matrix cannot be compressedwithout fracturing. The fracturing of the structural matrix can diminishthe final strength of the sheet even if the fractures are microscopicand not visible to the naked eye. The compaction process of a dry sheetmay be improved by spraying the surface of the sheet with water, whichprovides the sheet with adequate moisture and also fixes and aligns thecompacted particles within the sheet surface.

It may also be preferable to further alter the surface of thehydraulically settable sheet by passing the sheet between one or morepairs of finishing rollers. For example, in order to create a sheet witha very smooth surface on one or both sides, the sheet may be passedbetween a pair of hard and soft rollers.

In other embodiments, the finishing rollers can impart a desiredtexture, such as a meshed or checkered surface. Instead of using a hardand a soft roller, rollers which can imprint the sheets with the desiredfinish may be used.If desired, the rollers can imprint the surface ofthe sheet with a logo or other design. Special rollers capable ofimparting a water mark can be used alone or in conjunction with any ofthese other rollers.

It may be desired to corrugate the sheets in a manner similar tocorrugated cardboard. This is accomplished by passing a semi-moist sheetbetween a pair of corrugated rollers. The moisture content of the sheetshould be controlled so that the corrugation process does not result ina sheet with a damaged structural matrix. This may typically be carriedout using steam.

(e) Scoring

In some cases it may be desirable to alternatively score, score cut, orperforate the sheet in order to define a line upon which the sheet mayfold or bend. A score cut can be made by using a sharp knife blademounted on a score press or it can be accomplished using continuous diecut rollers. A score may be made in the sheet by means of a scoring die.Finally, a perforation may be made by means of a perforation knife.

The purpose of the score, score cut, or perforation is to create alocation on the hydraulically settable sheet where the sheet can be bentor folded. This creates a "hinge" within the sheet with far greaterbendability and resilience than possible with an unscored orunperforated hydraulically settable sheet. In some cases multiple scorecuts or perforations may be desirable.

Cutting a score line or perforation within the sheet creates a betterfold line or hinge for a number of reasons. First, it provides a placewhere the sheet might more naturally bend or fold. Second, cutting ascore makes the sheet at the score line thinner than the rest of thesheet, which reduces the amount of lengthwise elongation of the surfacewhile bending the sheet. The reduction of surface elongation reduces thetendency of the structural matrix to fracture upon being folded or bent.Third, the score cut or perforation allows for a controlled crackformation within the matrix the event that fracture of the structuralmatrix occurs.

It may sometimes be preferable to concentrate more fibers at the placein which the score cut or perforation be made. This can be accomplishedby co-extruding a second layer of hydraulically settable materialcontaining a higher fiber content at predetermined timed intervals tocorrespond with the location of the score cut or perforation. Inaddition, fibers can be placed on top of, or injected within, the sheetduring the extrusion or calendering processes order to achieve a higherfiber concentration at the desired location.

The hydraulically settable sheet will preferably be in a substantiallydry or semi-hardened state during the scoring or perforation process.This is desirable to prevent the score or perforation from closing upthrough the migration of moist material into the score cut. Sincescoring generally (and perforation always) involves cutting through aportion of the structural matrix, the sheet can even be totally drywithout the scoring or perforation process harming the sheet. However,in cases where a score is pressed rather than cut into the sheetsurface, the sheet should be moist enough to prevent fracture due to thedislocation of the structural matrix.

In most cases where a thinner sheet (<1 mm) is being score cut, the cutwill have a depth relative to the thickness of the sheet that is withinthe range from between about to about 50%, more preferably within therange from between about 20% to about 35%. In the case of thickersheets, the score cut will usually be deeper due to the decrease inbendability of the thicker sheet.

As discussed below, it may be desirable to coat the sheet or to applyprint or other indicia on the surface of the sheet. This can beaccomplished using printing means known the art of printing paper orcardboard products. Because the sheets have a relatively high porositylike paper or cardboard, the applied ink will tend to dry rapidly. Inaddition, decals, labels or other indicia can be attached or adhered thecementitious sheet using methods known in the art.

Finally, the substantially hardened sheets can be immediately used toform containers or other objects, or they may be stored until neededsuch as, for example, by winding the sheets into a roll or cutting andstacking individual sheets into a pile. The hydraulically settablesheets made according to the processes set forth above can then be usedjust like paper or cardboard and can be fashioned into endless varietyof containers or other useful objects, even in manufacturing equipmentwhich is currently used with paper or cardboard.

The sheets or continuous rolls of hydraulically settable materialmanufactured by the foregoing process can be utilized in existingequipment to make a variety of food and beverage containers. Sheets ofsuch material have be used in conventionally available cup and packagemaking equipment which were designed for use with paper. In light of thesimilar functional characteristics of the dried sheets of hydraulicallysettable compositions of the present invention to paper, they can besubstituted in most equipment for paper. Those modifications which mustbe made in the container manufacturing and processing operations havebeen found to be easily within the skill of those in the art.

5. The Post-Molding and Curing Processes (a) Coating

It may desirable to coat the hydraulically settable products preparedusing the processes set forth above. Coatings can be used to alter thesurface characteristics of the hydraulic product in a number of ways.They may provide protection against moisture, base, acid, or oil-basedsolvents. They may also provide a smoother or glossier surface. They mayeven reinforce the hydraulically settable product, particularly at abend or fold line in a sheet material that has been formed into acontainer.

Some coatings can be applied to the surface of the product during thesheet forming or product molding process, in which case the process isan "on-machine" process. In an on-machine process, the coating may beapplied as a liquid, gel, or even a thin film sheet. It may bepreferable to apply the coating after the hydraulic product has beenformed and dried to at least a limited extent, in which case the processis an "off-machine" process.

The object of the coating process is usually to achieve a uniform filmwith minimum defects on the surface of product. The selection of aparticular coating process depends on a number of substrate variables,as well as coating formulation variables. The substrate variablesinclude the strength, wettability, porosity, density, smoothness, anduniformity of the matrix of the product. The coating formulationvariables include total solids content, solvent base (including watersolubility and volatility), surface tension, and rheology. Coatingprocesses known in the art that may be used to coat the hydraulicallysettable sheets or products the present invention include spraying,blade, puddle, air-knife, printing, and gravure coating.

(b) Stacker/Accumulator

A custom automatic stacker can be installed at the end of themanufacturing line to create sets of stacks. The stacks are loaded ontoa rotary table which allows a manual removal of the stack cups andplacement into the downstream printing step.

(c) Printing

Another optional step in the manufacturing process is applying print ordesigns to the container through the use of a conventional printer, suchas an offset, Van Dam, laser, direct transfer contact, and thermographicprinters. However, essentially any hand or mechanical means can be used.Of coarse, hydraulically settable products such as those disclosedherein are particularly well suited for such a use. Furthermore, asmentioned above, it is within the scope of the present invention to coatthe containers with a government approved coating, most of which arecurrently used and well adapted for placing indicia thereon. One skilledin the are will appreciate that sheet porosity and ink quantities mustbe compatible.

(d) Bagging/Cartonizing

Prior to shipping the containers they must be properly packaged.Accordingly, the finished stacks of cups are taken off the printer andmanually loaded into poly bags and then loaded into cartons.

(e) Palletizing

The finished cartons are then collected, sealed, marked, stacked andwrapped in standard carton handling/palletizing equipment for subsequentshipment.

III. Examples of the Preferred Embodiments

To date, numerous tests have been performed comparing the properties ofcontainers of varying composition. Below are specific examples ofcementitious compositions which have been created according to thepresent invention.

Example 1

A cementitious cup was formed by jiggering a cementitious mixturecontaining the following components:

    ______________________________________                                        Portland White Cement  2.0    kg                                              Water                  1.004  kg                                              Perlite                0.702  kg                                              Tylose ® 4000      60     g                                               ______________________________________                                    

The portland cement, Tylose®, and perlite were mixed for about 2minutes; thereafter, the water was added and the mixture was blended foran additional 10 minutes. The resultant cementitious mixture had awater-to-cement ratio of approximately 0.5. The concentration of cementpaste (cement and water) in this mixture was 79.8% by weight, withperlite comprising 18.6%, and the Tylose® being 1.6% by weight of thecementitious mixture.

The resultant cementitious material was then cast by jiggering into theshape of a cup. This cup had a wall thickness of 4.5 mm, and wouldinsulate to 65° C., which means that the maximum temperature on theoutside of the cup would be 65° C. when the cup is filled with hot water(88° C.). The cup was designed to have a predetermined bulk density byadding a porous aggregate (in this case perlite).

Another porous aggregate such as calcium silicate microspheres or hollowglass spheres can be used (as seen in later examples). Because porousaggregates have a low specific gravity, they can impart a degree ofinsulation ability to the material within the containers. This and laterexamples demonstrate that it is possible to manufacture a lightweightcontainer from cement which can be designed to have adequate insulationfor a particular purpose. Because increasing the insulative effect ofthe container generally accompanies a reduction in strength, it ispreferable to design the material to have only that range of insulationnecessary for a given purpose. In addition, later examples will showthat the container design can be altered in order to obtain anadequately insulating container without increasing the actual insulatingeffect of the material within the container.

In this first example, the relatively large wall thickness of the cupsresulted from an attempt to make the cups more insulating, not becausethe thickness was necessary in order for the cup to have adequatestrength. However, the resulting cementitious cup had a good surfacefinish and was easily cast by jiggering. While the cup was relativelydense (having a bulk specific gravity of about 1.6), it did demonstratethe concept that a cementitious mixture can be designed to have formstability in the green state and still be molded by conventional means.

Example 2

A cementitious cup was formed by jiggering a cementitious mixturecontaining the following components:

    ______________________________________                                        Portland White Cement   2.0    kg                                             Water                   1.645  kg                                             Perlite                 0.645  kg                                             Tylose ® 4000       20     g                                              Tylose ® FL 15002   15     g                                              Cemfill ® glass fibers (4.5 mm)                                                                   370    g                                              ______________________________________                                    

The cementitious mixture was prepared utilizing the procedures set forthwith respect to Example 1, except that the fibers were added aftermixing the cement, water, Tylose®, and perlite for about 10 minutes. Thecombined mix was then mixed for an additional 10 minutes. The resultantcementitious mixture had a water-to-cement ratio of approximately 0.82.The concentration of cement paste (cement and water) in this mixture was77.6% by weight, with perlite comprising 13.7%, the Tylose® 4000 and FL15002 comprising 0.43% and 0.32%, respectively, and the glass fibersbeing 7.9% by weight of the cementitious mixture.

The resultant cementitious mixture was then cast by jiggering into theshape of a cup. The cup had good surface finish, like the cup of Example1, but it also had a higher toughness and fracture energy than the cupof Example 1 because of the addition of the glass fibers. The cups soobtained demonstrated an adequate amount of strength, and did not breakwhen dropped onto a concrete or marble floor from heights of up to 2meters, as would have been expected when dropping thin-walledcementitious objects from this height.

Example 3

A cementitious cup was formed by jiggering an extruded cementitiousmixture containing the following components:

    ______________________________________                                        Portland White Cement   4.0    kg                                             Water                   1.179  kg                                             Calcium silicate microspheres                                                                         1.33   kg                                             Tylose ® FL 15002   30     g                                              Cemfill ® glass fibers                                                                            508    g                                              (4.5 mm; alkali resistant)                                                    ______________________________________                                    

The cementitious mixture was prepared utilizing the procedures set forthwith respect to Example 2, except that the microspheres were added inplace of the perlite. The resultant cementitious mixture had awater-to-cement ratio of approximately 0.29, which is dramatically lowerthan that of Examples 1 and 2. This demonstrates that, depending uponthe aggregate system, significantly different water to cement ratios canbe designed into the composition. The concentration of cement paste(cement and water) in this mixture was 73.5% by weight, with themicrospheres comprising 18.9%, the Tylose® comprising 0.43%, and theglass fibers being 7.2% by weight of the cementitious mixture.

The resulting cementitious cup did not have as good a surface finish asExamples 1 and 2, but it was lighter. The cementitious mixture could bereadily jiggered and extruded and would insulate hot water to 63° C.

While early prototypes of the present invention, cups prepared accordingto Examples 1-3 taught that the concepts tested therein were sound.These examples taught that adding porous, lightweight aggregates to thecementitious mixture alone does not generally result in a materialhaving the same insulation ability as polystyrene. Neither addition ofperlite, nor the calcium silicate microspheres imparted the degree ofinsulation desired for commercial use with coffee and other hot drinkswithin the mix designs used in these examples. Therefore, methods ofimparting insulation other than by merely adding inorganic materials tothe cement matrix were explored.

In the next series of examples, finely dispersed, microscopic,discontinuous air voids were introduced into the hydraulically sortablestructural matrix, which had the effect of greatly increasing theinsulative ability of the cup.

Example 4

A cementitious cup was formed by jiggering a cementitious mixturecontaining the following components:

    ______________________________________                                        Portland White Cement  2.52   kg                                              Water                  1.975  kg                                              Vermiculite            1.457  kg                                              Vinsol resin           2.5    g                                               Tylose ® 4000      25     g                                               Tylose ® FL 15002  75     g                                               Abaca fiber            159    g                                               ______________________________________                                    

The cementitious mixture was prepared by prewetting the abaca fiber(which had been pretreated by the manufacturer with sodium hydroxide sothat greater than 85% of the cellulose was α-hydroxycellulose) and thencombining the fibers with each of the other components exceptvermiculite. This mixture was mixed for about 10 minutes, and then mixeda further 10 minutes after the vermiculite was added. The resultantcementitious mixture had a water-to-cement ratio of approximately 0.78.The concentration of cement paste (cement and water) in this mixture was72.3% by weight, with the vermiculite comprising 23.4%, the Tylose® 4000and FL 15002 comprising 0.40% and 1.21%, respectively, the vinsol resin(an air entraining agent) comprising 0.04%, and the abaca fibers being2.6% by weight of the cementitious mixture.

The cup made in Example 4 was cast by jiggering to have a wall thicknessof about 2.5 mm, which is substantially thinner than the wallthicknesses obtained for the cups in Examples 1-3. Nevertheless, thecementitious cup of Example 4 was able to insulate down to 62° C. (asignificant improvement over the earlier cups in light of the reducedwall thickness). The surface finish was very smooth, and the cup had ahigh toughness and fracture energy. The cup had a capacity of about 390cc and weighed about 95 g.

Example 5

A cementitious cup was formed by jiggering a cementitious mixturecontaining the following components:

    ______________________________________                                        Portland White Cement  2.52   kg                                              Water                  2.31   kg                                              Vermiculite            2.407  kg                                              Vinsol resin           2.5    g                                               Tylose ® 4000      25     g                                               Tylose ® 15002     75     g                                               Abaca fiber            159    g                                               Aluminum (<100 mesh)   0.88   g                                               ______________________________________                                    

The cementitious mixture was made utilizing the procedures set forthwith respect to Example 4. The resultant cementitious mixture had awater to cement ratio of approximately 0.92. This mixture was readilycast by jiggering, even though it had a relatively high water-to-cementratio. The concentration of cement paste (cement and water) in thismixture was 64.4% by weight, with the vermiculite comprising 32.1%, theTylose® 4000 and 15002 comprising 0.33% and 1.0%, respectively, thevinsol resin (an air entraining agent) comprising 0.03%, the abacafibers being 2.1%, and the amount of aluminum being about 0.01% byweight of the cementitious mixture.

The addition of aluminum resulted in the incorporation of finelydispersed hydrogen bubbles within the cementitious mixture. Hence, theresultant cup was even more lightweight and porous than the cup ofExample 4, weighing only 85 g. The cup further had a smooth surfacefinish and there was no degradation in the toughness, fracture energy,or insulation capability.

Example 6

A cementitious cup was formed by jiggering a cementitious mixturecontaining the following components:

    ______________________________________                                        Portland White Cement  2.52   kg                                              Water                  1.65   kg                                              Vermiculite            1.179  kg                                              Perlite                0.262  kg                                              Vinsol resin           5.0    g                                               Tylose ® 4000      12.5   g                                               Tylose ® FL 15002  37.5   g                                               Abaca fiber            159    g                                               Aluminum (<100 mesh)   1.5    g                                               ______________________________________                                    

The cementitious mixture was made utilizing the procedures set forthwith respect to Example 4. The resultant cementitious mixture had awater-to-cement ratio of approximately 0.65. The concentration of cementpaste (cement and water) in this mixture was 71.6% by weight, with theperlite comprising 4.5%, the vermiculite comprising 20.2%, the Tylose®and 15002 comprising 0.21% and 0.64%, respectively, the vinsol resin (anair entraining agent) comprising 0.086%, t:he abaca fibers being 2.7%,and the amount of aluminum being about 0.026% by weight of thecementitious mixture.

The resulting cementitious cup had properties and characteristicssubstantially similar to those of the cup made in Example 5.

The cups of Examples 4-6 yielded better results, both in terms ofstrength and, especially, insulative ability compared to cups in theprevious examples. Cups made in Examples 4-6 were able to insulate to62° C. These examples demonstrate that the incorporation of microscopicair voids can greatly increase the container's insulating abilitywithout appreciably decreasing the strength. They also show thataluminum can be used to generate the air bubbles which are entrainedwithin the cementitious mixture.

These and other experiments have shown that perlite tends to reduce thestrength of the container, while imparting the same level of insulationregardless of how the cement paste was either mixed or molded. On theother hand, because vermiculite is plate-shaped, it is advantageous,both in terms of strength and insulation, to align the individualparticles along parallel planes within the wall of the container. Thismay be achieved by jiggering, ram pressing, extrusion, or rolling themixture.

Similarly, in order for the added fibers to be most effective, it hasbeen found advantageous to align them within the hydraulically settablestructural matrix as well. This may also be achieved using theabove-mentioned molding processes. Such alignment imparts much greaterstrength and toughness to the resulting food or beverage container.

It has also been discovered that where a more viscous hydraulic paste isinvolved, it takes from between 5 and 10 minutes of mixing to obtaingood flocculation of the cement paste and the resulting plasticbehavior. In addition, takes Tylose® about 5 minutes to "react" with orgel in the presence of water in order to impart its thickening effect tothe mixture.

Examples 7-10

Cementitious plates were formed by passing, through a pair of rollers,various cementitious mixtures containing hollow glass spheres (diameter<100 microns) as the aggregate. The components for each example was asfollows:

    ______________________________________                                                                    Tylose ®                                                                         Glass                                      Example  Cement   Water     FL 15002                                                                             Spheres                                    ______________________________________                                        7        4 kg     2.18 kg   200 g  445 g                                      8        3 kg     1.85 kg   150 g  572 g                                      9        2 kg     1.57 kg   100 g  857 g                                      10       1 kg     1.55 kg   100 g  905 g                                      ______________________________________                                    

The cementitious mixtures were prepared by first combining the hydrauliccement, Tylose®, and water together using a high shear mixer for 5minutes. Thereafter, the glass spheres were added and mixed for 5minutes using a low shear mixer. The resultant cementitious mixtures inExamples 7-10 had water to cement ratios of approximately 0.55, 0.62,0.79, and 1.58, respectively. Even with the high water to cement ratioof Example 10, the cementitious mixture was form stable in the greenstate and readily moldable. The percentage by weight of the glassspheres in each of Examples 7-10 was 6.5%, 10.3%, 18.9%, and 25.3%,respectively.

These materials were extremely lightweight, having densities in therange from about 0.25 to 0.5. Equally important were the insulativecapabilities of cups made from these mixtures having a wall thickness of2.0 mm, as measured by the maximum temperature achieved by the outerwall of the cup when 88° C. water was placed inside the cups:

    ______________________________________                                        Example     Insulation Temperature                                            ______________________________________                                        7           62° C.                                                     8           55° C.                                                     9           56° C.                                                     10          57° C.                                                     ______________________________________                                    

It is believed that the insulation ability of the products of Examples 9and 10 are even greater than indicated. These cups were coated withmelamine before they were tested and the solvent in the melamine mayhave made the effective thickness of the cups less than 2.0 mm. In fact,2.0 mm thick sheets were placed in an oven at 150° C. for three hours;thereafter, they could be removed by hand. This means that the surfacetemperature was significantly less than 60° C., which may be due to therelatively low specific heat of the lightweight cementitious materialsmade in these examples.

Examples 11-14

The cementitious mixtures of Examples 7-10 were altered by addingvarying amounts of abaca fiber, which were blended in during the highshear mixing step.

    ______________________________________                                                     Corresponding                                                                             Amount of                                            Example      Example     Abaca fiber                                          ______________________________________                                        11           7           149 g                                                12           8           152 g                                                13           9           180 g                                                14           10          181 g                                                ______________________________________                                    

The resultant percentage by weight of the abaca fibers in Examples 11-14was 2.1%, 2.7%, 3.8%, and 4.8%, respectively. These cementitiousmaterials were as lightweight and insulative as those made in Examples7-10, but were much tougher and had a higher fracture energy. Inaddition, adding more fibers made the products more bendable, as incontainers having hinged flaps or other closure mechanisms. Hence, theuse of these abaca fibers, as well as other types of fibers, isparticularly desirable in situations where such characteristics aredesirable.

Examples 15-17

Plates and cups composed of cementitious mixtures of these examples wereprepared according to the procedures, and using the components, ofExample 7 (i.e., 4 kg of portland white cement is used) with theexceptions that aluminum powder (<100 mesh) and NaOH were added to thecementitious mixtures in the following amounts and the resultant moldedplates were heated to about 80° C. for 30-60 minutes:

    ______________________________________                                        Example        Aluminum  NaOH                                                 ______________________________________                                        15             4 g       21.9 g                                               16             6 g       34.7 g                                               17             8 g       34.7 g                                               ______________________________________                                    

The NaOH was added to the cementitious mixture to activate the aluminumby establishing a pH in the preferable range of about 13.1-13.8. Theporosity of the cementitious mixture was increased, the bulk density wasdecreased, insulation capability was increased, and the plates and CUDSwere more lightweight. The rate and extent of the reaction aluminummetal can be altered by adjusting the amount aluminum and heat that areadded. As more of each is added, the material becomes lighter, fluffierand softer, making good cushioning material.

It is important to note that shrinkage cracks were not observed in theplates of Examples 15-17, even though the cementitious mixtures wereheated and much of the water was driven off rapidly.

Examples 18-20

Cementitious plates were formed by passing, through a pair of rollers,cementitious mixtures containing the components for each example asfollows:

    ______________________________________                                        Example  Aluminum     NaOH    Abaca Fibers                                    ______________________________________                                        18       10.0 g       22.3 g  60 g                                            19       15.0 g       22.3 g  60 g                                            20       22.5 g       22.3 g  60 g                                            ______________________________________                                    

In each of these examples, there was 4 kg of portland white cement, 1.4kg of water, and 40 g of Tylose® FL 15002. The cementitious mixtureswere prepared substantially according to the procedures set forth inExample 1, with the exception that fibers rather than perlite aggregateswere added. Like the cementitious mixtures of Examples 15-17, thesematerials are extremely lightweight and are very insulative because ofthe amount of air that was incorporated into the hydraulically settablemixtures. However, the cementitious mixtures of these examples haveincreased toughness and fracture energy because of the addition of thefibers.

Examples 21-24

Cementitious plates were formed by passing, through a pair of rollers,cementitious mixtures containing the components for each example asfollows:

    ______________________________________                                        Glass Spheres                                                                 Example                                                                              Fine    Medium   Coarse Aluminum NaOH                                  ______________________________________                                        21     133 g   317 g    207 g  4.0 g    19.7 g                                22     133 g   317 g    207 g  6.0 g    31.2 g                                23     133 g   317 g    207 g  8.0 g    31.2 g                                24     133 g   317 g    207 g  0.0 g      0 g                                 ______________________________________                                    

In each of these examples, there was 4 kg of portland white cement and1.96 kg of water; hence, the water-to-cement ratio was 0.49. The amountsof Tylose® FL 15002 and abaca fibers in each mixture were 200 g and 60g, respectively. The cementitious mixtures were prepared substantiallyaccording to the procedures set forth in Examples 15-17, with theexception that hollow glass spheres having three different diameterswere used. All of the glass spheres were less than one millimeter.(Example 24, however, does not incorporate aluminum and NaOH.)

The percentage by weight of the total amount of glass spheres in each ofthe cementitious mixtures of Examples 21-24 was 2.1%.

The cementitious mixtures were also pressed into the shape of a cupusing male and female molds. The cups had similar properties as theplates and demonstrate the viability of molding the cementitious mixtureinto the shape of a container.

These materials were extremely lightweight (density <0.7) and were veryinsulative because of the amount of air and the effective packing of theglass spheres incorporated into the mixtures. The cementitious mixturesof these examples demonstrated the value of packing the aggregates inorder to maximize their effect in the resultant composition While thecementitious mixture of Example 24 is a good composition for manycircumstances, its insulative capabilities are not as great as thecementitious mixtures of Examples 21-23.

Examples 25-28

Cementitious plates were formed by passing, through a pair of rollers,cementitious mixtures containing thecomponents for each example asfollows:

    ______________________________________                                        Glass Spheres                                                                 Example                                                                              Fine    Medium   Coarse Aluminum NaOH                                  ______________________________________                                        25     171 g   394 g    267 g  3.0 g    16.7 g                                26     171 g   394 g    267 g  4.5 g    26.6 g                                27     171 g   394 g    267 g  6.0 g    26.6 g                                28     171 g   394 g    267 g  0.0 g      0 g                                 ______________________________________                                    

In each of these examples, there was 3 kg of portland white cement and1.67 kg of water; hence, the water-to-cement ratio was 0.56. Tylose® FL15002 and abaca fibers were added to each mixture in amounts of 150 gand 60 g, respectively. The percentage by weight of the total amount ofglass spheres in each of the cementitious mixtures of Examples 25-28 was3.4%. Otherwise, the cementitious mixtures in these examples wereprepared substantially according to the procedures of Examples 21-24.

The materials that were made in these examples are extremely lightweightand very insulative because of the amount of air and the effectivepacking of the glass spheres incorporated into the mixtures. Thecementitious mixtures of these examples show the value of packing theaggregates in order to maximize their effect in the resultantcomposition. While the cementitious mixture of Example 28 is acomposition for many circumstances, it does not demonstrate the sameinsulative capabilities as the cementitious mixtures of Examples 25-27.

The plates of Examples 25-28 are lighter and more insulating than thecorresponding plates of Examples 21-24. However, these plates have lessstrength than those with greater amounts of cement.

Examples 29-32

Cementitious plates were formed by passing, through a pair of rollers,cementitious mixtures containing the components for each example asfollows:

    ______________________________________                                        Glass Spheres                                                                 Example                                                                              Fine    Medium   Coarse Aluminum NaOH                                  ______________________________________                                        29     257 g   591 g    400 g  2.0 g    14.2 g                                30     257 g   591 g    400 g  3.0 g    22.5 g                                31     257 g   591 g    400 g  4.0 g    22.5 g                                32     257 g   591 g    400 g  0.0 g      0 g                                 ______________________________________                                    

In each of these examples, there was 2 kg of portland white cement and1.41 kg of water; hence, the water-to-cement ratio was 0.71. Tylose® FL15002 and abaca fibers were added to each mixture in amounts of 100 gand 60 g, respectively. The percentage by weight of the total amount ofglass spheres in each of the cementitious mixtures of Examples 29-32 was6.8%. Otherwise, the cementitious mixtures were prepared substantiallyaccording to the procedures of Examples 29-32.

The materials that were made in these examples are extremely lightweightand very insulative because of the amount of air and the effectivepacking of the glass spheres incorporated into the mixtures. Thecementitious mixtures these examples show the value of packing theaggregates order to maximize their effect in the resultant composition.While the cementitious mixture of Example 32 is a good composition formany circumstances, it does not demonstrate the same insulativecapabilities as the cementitious mixtures of Examples 29-31.

The plates of Examples 29-32 are even lighter and more insulating thanthe corresponding plates of Examples 21-28. However, these plates haveless strength that those with greater amounts of cement.

Examples 33-36

Cementitious plates were formed by passing, through a pair of rollers,cementitious mixtures containing the components for each example asfollows:

    ______________________________________                                        Glass Spheres                                                                 Example                                                                              Fine    Medium   Coarse Aluminum NaOH                                  ______________________________________                                        33     271 g   624 g    422 g  1.0 g    14.3 g                                34     271 g   624 g    422 g  1.5 g    22.6 g                                35     271 g   624 g    422 g  2.0 g    22.6 g                                36     271 g   624 g    422 g  0.0 g      0 g                                 ______________________________________                                    

In each of these examples, there was 1 kg of portland white cement and1.42 kg of water; hence, the water-to-cement ratio was 1.42. Tylose® FL15002 and abaca fibers were added to each mixture in amounts of 100 gand 60 g, respectively. The cementitious mixtures were preparedsubstantially according to the procedures of Examples 21-24. Even thoughthe water-to-cement ratio of these cementitious mixtures was very high,they were readily extruded and cast by jiggering.

The percentage by weight of the total amount of glass spheres in each ofthe cementitious mixtures of Examples 33-36 was 9.7%.

These materials are extremely lightweight and are very insulativebecause of the amount of air and the effective packing of the glassspheres incorporated into the mixtures. The cementitious mixtures ofthese examples show the value of packing the aggregates in order tomaximize their effect in the resultant composition. While thecementitious mixture of Example 36 is a good composition for manycircumstances, it does not demonstrate the same insulative capabilitiesas the cementitious mixtures of Examples 33-35.

The plates of Examples 33-36 are still more insulating and lighter thanthe corresponding plates of Examples 21-32. However, these plates haveless strength than those with greater amounts of cement.

Examples 37-38

Cementitious mixtures containing the following components were used tomake cementitious sheets:

    ______________________________________                                                                 Tylose ®                                                                         Abaca                                         Example                                                                              Cement   Water    FL 15002                                                                             Fibers Surfactant                             ______________________________________                                        37     10 kg    23.0 kg  300 g  200 g  300 g                                  38     10 kg    20.0 kg  300 g  200 g  300 g                                  ______________________________________                                    

In these examples, microfine cement was utilized to make thecementitious sheets. The cementitious mixtures were made by mixing thecomponents for about 10 minutes in a high energy mixer of the typediscussed above, which is available from E. Khashoggi Industries. Thishigh energy and high speed mixer introduced significant amounts of airinto the cementitious mixtures; this air was entrained within thecementitious mixture by use of the surfactant and stabilized by theTylose®. The resulting cementitious mixtures were passed between a pairof rollers and formed into thin sheets (1 mm). The sheets were thenscored, folded into the shape of a cereal box, and glued together usingadhesive techniques known in the art. These products were alternativelyhardened by passing them through a heat tunnel, which helped to removeexcess water and to increase their green strength.

Examples 39-40

Cementitious mixtures containing the following components were used tomake cementitious sheets:

    ______________________________________                                                                Tylose ®                                                                         Graphite                                       Example                                                                              Cement   Water   FL 15002                                                                             Fibers  Surfactant                             ______________________________________                                        39     4.23 kg   8.1 kg 120 g  260 g   135 g                                  40     10.0 kg  20.0 kg 300 g  300 g   300 g                                  ______________________________________                                    

In these examples, microfine cement was utilized. Like the products ofExamples 37 and 38, the cementitious mixtures of these examples weremade by mixing the components for about 10 minutes in a high shear mixerof the type discussed above, which is available from E. KhashoggiIndustries. This high shear, high speed mixer introduced significantamounts of air into the cementitious mixtures; this air was entrainedwithin the cementitious mixture by the surfactant.

However, due to the graphite fibers, the mixture was not as easilyfoamed and was not as lightweight and insulative as materials containingno graphite fibers. The resulting cementitious mixtures were passedbetween a pair of rollers and formed into thin sheets (1 mm), which werefolded into the shape of a cereal box and glued together using adhesivetechniques known in the art. These products were alternatively hardenedby passing them through a heat tunnel, which helped to remove excesswater and to increase their green strength.

The resulting cementitious materials were also highly insulative and hada low bulk specific gravity in the range of about 0.25-0.4.

Example 41

A cementitious plate was formed from a cementitious mixture using theprocedure set forth in Example 37, with the exception that about 1.2 kgof glass spheres was added to the "foamed" mixture of cement, water, andTylose®. The resultant plate had an insulative ability not significantlydifferent from standard polystyrene foam plates. The plate of thisexample was placed in an oven for three hours at 150° C. and could stillbe removed with bare fingers.

Example 42

Thin cementitious sheets were formed by molding a cementitious mixturewhich included the following:

    ______________________________________                                        Portland White Cement   1.0     kg                                            Water                   2.5     kg                                            Tylose ® FL 15002   200     g                                             Hollow Glass Spheres (<100 microns)                                                                   1.0     kg                                            Abaca Fiber             5% by volume                                          ______________________________________                                    

The cementitious mixture was made by prewetting the abaca fiber (whichwas pretreated by the manufacturer so that greater than 85% of thecellulose is α-hydroxycellulose) ant then adding the excess water andthe fibers to a mixture of Tylose® and portland cement. This mixture wasmixed at relatively high speed for about 10 minutes, and then at arelatively slow speed for 10 minutes after the hollow glass spheres wereadded. The resulting cementitious mixture had a water to cement ratio ofapproximately 2.5.

This mixture was passed between a pair of rollers and formed into thinsheets of about 1 mm in thickness. Wet sheets were scored and thenfolded in an attempt to create a box. However, there was a fair amountof splitting and a box with sufficient strength and integrity could notbe formed.

Thereafter, sheets were first allowed to harden and then were scored,folded into the shape of a box, and glued together by adhesive meanswell known in the paper art. The amount of splitting at the fold wasnegligible, which demonstrated that it is preferable to score and thenfold the thin sheets after they have been allowed to harden or solidifysomewhat. The thin sheets were formed into a box that had the shape,look and weight of a dry cereal box used presently as manufactured fromcardboard stock.

Example 43

The dried sheets formed in Example 42 were cut into appropriate shape,rolled to form a cup, and glued using adhesive means known in the art.Examples 42 and 43 demonstrate that it is possible to make boxes, cups,or other containers of similar shape which are presently made fromcardboard, paper, or plastic.

The following examples demonstrate that flexible cementitious materialshaving high toughness and strength can be manufactured. They are usefulin containment applications where cushioning and flexibility areimportant criteria.

Examples 44-48

Flexible sheets were formed from cementitious mixtures containing thefollowing:

    ______________________________________                                        Example                                                                              Plastic Spheres                                                                            Cement   Water   Tyloses ®                            ______________________________________                                        44     0.12 kg      1.0 kg   2.0 kg  0.1 kg                                   45     0.1213 kg    0.8 kg   2.0 kg  0.1 kg                                   46     0.1225 kg    0.6 kg   2.0 kg  0.1 kg                                   47     0.1238 kg    0.4 kg   2.0 kg  0.1 kg                                   48     0.1251 kg    0.2 kg   2.0 kg  0.1 kg                                   ______________________________________                                    

The "plastic spheres" are made from polypropylene and have averageparticle sizes less than 100 microns and an average density of 0.02g/cm³. The cementitious mixtures were mixed and then formed into sheetsaccording to the procedure set forth in Example 42. The cementitioussheets were relatively strong and very flexible compared to previous mixdesigns. The compressive strength of the plate made according to Example44 was 2 MPa and the tensile strength was 1 MPa. The surprising featureis that the compressive and tensile strengths are of the same magnitude,which is very unusual for most cement products. Usually the compressivestrength is far greater than the tensile strength. As less cement isadded, the compressive and tensile strengths decrease in increments,with the plate of Example 48 having a tensile strength 0.5 MPa.

These packaging materials could be physically compressed withoutcrumbling like their nonflexible, cementitious counterparts in earlierexamples, even when subject to forces that were greater than forcesnormally experienced by styrofoam containment materials. The flexiblecementitious materials were alternatively extruded into the shaperectangular shaped bars, which more dramatically demonstrated the degreeof flexibility made possible by this mixture.

The densities of the cementitious packaging materials made in theseexamples ranged between 0.1 and 0.6 g/cm³, with the density decreasingas less cement is used.

Examples 49-53

Flexible cementitious container materials were made according toExamples 44-48, except that prewetted abaca fibers were added to thecementitious mixture in the following amounts, as measured by unitvolume:

    ______________________________________                                        Example      Abaca Fiber                                                      ______________________________________                                        49           2%                                                               50           4%                                                               51           6%                                                               52           8%                                                               53           10%                                                              ______________________________________                                    

The fibers were well dispersed throughout the cementitious mixture usinga high shear mixer. The resulting cementitious plates and rectangularbars made therefrom Lad substantially the same densities andflexibilities as those in Examples 44-48, but with increasing tensilestrengths as the amount of abaca fiber was increased. The tensilestrengths of the materials formed herein ranged up to 5 MPa.

Example 54

Cementitious containers are formed using any of the compositions andprocedures set forth in Examples 44-53, except that the plastic spheresare concentrated near the surface of the cementitious mixture, yieldinga molded material in which the plastic spheres are concentrated at ornear the surfaces of the final hardened product. The container formedthereby has a higher concentration of plastic spheres near the surfaceof the cement matrix, where flexibility is more important, and virtuallyno plastic spheres in the center of the packaging material whereflexibility is less important. The advantage of this greater flexibilityat the surfaces with the same amounts less of plastic spheres in theoverall compositions. At the same time, the rigidity of the center ofthe container walls makes them as durable and tough as the more rigidcontainers above.

The next set of examples utilizes cementitious mixtures which have arelatively high specific gravity, but which are formed into solidobjects, such as honeycomb structures, that have a high amount ofintrastructural space. This reduces the bulk specific gravity of thefinal product so that it is more lightweight, yet very strong anddurable.

Example 55

A honeycomb container structure is extruded from a cementitious mixtureincluding the following:

    ______________________________________                                        Portland White Cement  4.0    kg                                              Fine Sand              6.0    kg                                              Water                  1.5    kg                                              Tyloses ® FL 15002 200    g                                               ______________________________________                                    

The cementitious mixture is formed by mixing the ingredients togetherfor 10 minutes using a high speed mixer to obtain a very homogeneousmixture. The cementitious mixture is then extruded to form a honeycombstructure which has very high compressive strength. Because of thehoneycomb structure, the cured material is very lightweight with adensity of only 1.02 g/cm³. Moreover, the cured material has acompressive strength of about 75 MPa. Depending upon the amount of spacewithin the honeycomb structure, the block density can easily rangeanywhere from between 0.5 to 1.6 g/cm³.

These materials can be used to form very strong, yet lightweight wallsof larger food or beverage packaging containers.

Examples 56-58

Cementitious mixtures are formed according to Example 55, except thatabaca fiber is included within the cementitious mixture in the followingamount, as measured by volume percent of the cementitious mixture:

    ______________________________________                                        Example      Abaca Fiber                                                      ______________________________________                                        56           1%                                                               57           2%                                                               58           3%                                                               ______________________________________                                    

The resulting honeycomb structures have high strength, both in the greenstate and after they are cured, due to the reinforcing effect of thehoneycomb structure. The honeycomb structures formed in these examplesare more ductile than in Example 55, while the compressive strengthswould be expected to be even greater. These materials can be used toform very strong, yet relatively lightweight walls of larger food andbeverage packaging containers.

Examples 59-61

Cementitious mixtures are formed according to Example 55, except thatfiber glass is included within the cementitious mixture in the followingamount, as measured by volume percent of the cementitious mixture:

    ______________________________________                                               Example                                                                              Fiber Glass                                                     ______________________________________                                               59     1%                                                                     60     2%                                                                     61     3%                                                              ______________________________________                                    

The resulting honeycomb structures have high strength, both in the greenstate and after they are cured, due to the reinforcing effect of thehoneycomb structure. The honeycomb structures formed in these examplesare more ductile than in Example 55, while the compressive strengthswould be expected to be even greater. These materials can be used toform very strong, yet relatively lightweight walls of larger food andbeverage packaging containers.

Example 62

Using any of the foregoing compositions, corrugated cementitious sheetscontaining a fluted inner structure sandwiched between two flat sheetsare formed. The flat outer sheets are formed by calendering a sheet ofthe material into a flat sheet of the appropriate thickness. Thecorrugated, or fluted inner sheet (which is similar to the fluted orcorrugated inner sheet of an ordinary cardboard box) is formed bypassing either a hardened or remoistened flat cementitious sheet of theappropriate thickness through a pair of rollers with intermeshingcorrugated surfaces or teeth.

Glue is applied to the surfaces of the corrugated sheet, which is thensandwiched between two flat sheets and allowed to harden.

Example 63

Using any of the foregoing compositions, the cementitious mixture ispressed or molded into the shape of a carton. Depending on thecomposition, the carton will exhibit high strength, durability,flexibility, low weight, and/or low density.

Example 64

Using any of the foregoing compositions, the cementitious mixture ismolded into the shape of a crate. This can be carried out by extruding ahoneycomb structure or corrugated sheet, or by molding any otherappropriate structure of adequate strength. Depending on thecomposition, the crate will exhibit high strength, durability,flexibility, low weight, and/or low density.

Example 65

Using any of the foregoing compositions, the cementitious mixture ismolded or pressed into the shape of a lid. Depending on the composition,the lid will exhibit high strength, durability, flexibility, low weight,and/or low density.

Example 66

Using any of the foregoing compositions, the cementitious mixture ismolded into the shape of a partition. Depending on the composition, thepartition will exhibit high strength, durability, flexibility, lowweight, and/or low density.

Example 67

Using any of the foregoing compositions, the cementitious mixture ismolded into the shape of a liner. Depending on the composition, theliner will exhibit high strength, durability, flexibility, low weight,and/or density.

Example 68

Using any of the foregoing compositions, cementitious mixture is moldedinto the shape of a box. This may be carried out by extrusion, and/orcalendering, and/or score cutting, and/or folding. Depending on thecomposition, the box will exhibit high strength, durability,flexibility, low weight, and/or low density.

Example 69

Using any of the foregoing compositions, the cementitious mixture isblow molded into the shape of a bottle. Depending on the composition,the bottle will exhibit high strength, durability, flexibility, lowweight, and/or low density.

Example 70

Using any of the foregoing compositions, the cementitious mixture ismolded into the shape of a utensil. Depending on the composition, theutensil will exhibit high strength, durability, flexibility, low weight,and/or low density.

Examples 71-88

Food and beverage containers were manufactured from cementitious sheetsof varying thicknesses formed from a cementitious mixture containing thefollowing components:

    ______________________________________                                        Portland Cement   1.0 kg                                                      Perlite           0.5 kg                                                      Mica              0.5 kg                                                      Fiber (Southern pine)                                                                           0.25 kg                                                     Tylose ® FL 15002                                                                           0.2 kg                                                      Water             2.5 kg                                                      ______________________________________                                    

The portland cement, mica, fiber, Tylose®, and water were mixed togetherin a high shear mixer for 5 minutes, after which the perlite was addedand the resulting mixture mixed for an additional 5 minutes in a lowshear mixer. The cementitious mixture was then placed into an augerextruder and extruded through a die having an opening in the shape of aslit. Continuous sheets were extruded which had a width of 300 mm and athickness of 6 mm.

The sheets were thereafter passed between one or more pairs of reductionrollers in order to obtain sheets having final thicknesses of 0.2 mm,0.3 mm, 0.4 mm and 0.5 mm, respectively. The rollers had a diameter of17 cm and were made of stainless steel coated with polished nickel toaid in preventing the cementitious mixture from sticking to the rollers.In addition, the rollers were heated to a temperature of 110° C. tofurther prevent sticking between the mixture and the rollers.

In order to obtain sheets having the desired thickness, the extrudedsheets were reduced in steps by using reduction roller pairs havingprogressively smaller gap distances between the rollers. The sheetthicknesses were reduced as follows:

    ______________________________________                                        6 mm → 2 mm → 0.5 mm →                                                         0.4 mm                                                  or                    0.3 mm                                                  or                    0.2 mm                                                  ______________________________________                                    

A combination of the extrusion process and the calendering processyielded sheets with substantially unidirectionally oriented fibers alongthe length (or direction of elongation) of the sheet. Because of this,the sheets had higher tensile strength in the lengthwise direction(10-12 MPa) compared to the widthwise direction (5-6 MPa).

The hardened cementitious sheets were finished, coated, and then formedinto a number of different food and beverage containers. For example, a"cold cup" (such as those in which cold soft drinks are dispensed atfast food restaurants) was made by cutting an appropriate shape from asheet, rolling the shape into the shape of a cup, adhering the ends ofthe rolled sheet using conventional water-based glue, placing a disc atthe bottom of the cup and then crimping the bottom of the rolled wallportion in order to hold the bottom in place, and curling the rim of thecup to strengthen the rim and create a smoother drinking surface. Sheetshaving thicknesses of 0.3 mm and 0.4 mm were used.

The amount of deflection when applying a constant force 1 inch below therim was comparable to conventional paper cups. The uncoated cementitiouscups did not leak when an aqueous solution containing methylene blue and0.1% surfactant was placed inside the cup for 5 minutes. Of course, anyleakage that may occur could be prevented by an appropriate coating.

A "clam shell" container (such as those presently used in the fast foodindustry to package hamburgers) was made by cutting an appropriate shapefrom a sheet, score cutting the sheet to form the desired fold lines,folding the sheet into the shape of a clam shell container, and adheringthe ends of the folded sheet (using both adhesive and interlocking flapmeans) to preserve the integrity of the container. Sheets havingthicknesses of 0.4 mm and 0.5 mm were used.

The sheet was found to more easily bend or close together on the side ofthe sheet opposite the score cut. It should be noted that normal scoresin conventional materials generally allow the sheet to more easily bendor close together on the side of the score. The resulting clam shellcontainers exhibited comparable or superior insulating ability comparedto paper clam shells.

A french fry container (such as those used to serve cooked french friesin the fast food industry) was made by cutting an appropriate shape froma sheet, score cutting the sheet to form the desired fold lines, foldingthe sheet into the shape of a french fry container, and adhering theends of the folded sheet using adhesive means to preserve the integrityof the container. Sheets having thicknesses of 0.25 mm, 0.3 mm, 0.35 mm,0.4 mm, 0.45 mm, and 0.5 mm were used to make the french fry containers.

A frozen food box (such as those used by supermarkets to package frozenfoods such as vegetables or french fries) was made by cutting anappropriate shape from a sheet, score cutting the sheet to form thedesired fold lines, folding the sheet into the shape of a frozen foodbox, and adhering the ends of the folded sheet using adhesive means topreserve the integrity of the box. Sheets having thicknesses of 0.25 mm,0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, and 0.5 mm were used to make thefrozen food boxes.

A cold cereal box was made by cutting an appropriate shape from a sheet,score cutting the sheet to form the desired fold lines, folding thesheet into the shape of a cold cereal box, and adhering the ends of thefolded sheet using adhesive means to preserve the integrity of thecereal box. Sheets having a thickness of 0.3 mm were used.

A straw was made by rolling a piece of a 0.25 mm sheet into the form ofa straw and adhering the ends together using adhesion means known in theart. In making the straw, as in making each of the containers set forthabove, it was advantageous to remoisten the sheet somewhat in order totemporarily introduce a higher level of flexibility into the sheet. Thisminimized splitting and tearing of the sheet. Nevertheless, the strawcould be rolled and crimped without the remoistening of the sheetwithout visible tearing and splitting.

The containers were found to break down in the presence of water overtime, with 1 day being the average time disintegration. The excess wastematerial that was trimmed from the sheets when making the containers waseasily recycled by simply breaking it up and mixing it back into thehydraulically settable mixture.

The various containers that were made are set forth as follows,including the thickness of the sheet used to make each container:

    ______________________________________                                        Example     Container   Sheet Thickness                                       ______________________________________                                        71          cold cup    0.3 mm                                                72          cold cup    0.4 mm                                                73          clam shell  0.4 mm                                                74          clam shell  0.5 mm                                                75          french fry box                                                                            0.25 mm                                               76          french fry box                                                                            0.3 mm                                                77          french fry box                                                                            0.35 mm                                               78          french fry box                                                                            0.4 mm                                                79          french fry box                                                                            0.45 mm                                               80          french fry box                                                                            0.5 mm                                                81          frozen food box                                                                           0.25 mm                                               82          frozen food box                                                                           0.3 mm                                                83          frozen food box                                                                           0.35 mm                                               84          frozen food box                                                                           0.4 mm                                                85          frozen food box                                                                           0.45 mm                                               86          frozen food box                                                                           0.5 mm                                                87          cold cereal box                                                                           0.3 mm                                                88          drinking straw                                                                            0.25 mm                                               ______________________________________                                    

Example 89

The cementitious sheets used to manufacture the containers in Examples71-88 could be printed using conventional printing presses used to printconventional paper sheets. The ink was able to dry as fast or fastercompared to when using conventional paper sheets. The printed sheetscould then be formed into any of the containers listed above the same aswithout being printed.

Example 90

A printed cementitious sheet obtained in Example 89 was formed into theshape of a cup according to the procedure set forth in Example 71,except that the top rim was treated with a mineral oil lubricant priorto the step of curling the top of the cup. Nevertheless, as above,curling was possible without mineral oil. The cup had all of thenecessary properties of weight, strength, and water resistance forcommercial use in the fast food industry, as well as includingidentifying information.

Example 91

Clam shell containers were made using the sheets made according toExamples 71-88. The sheets were tested to determine the optimum scorecut depth which would allow for the easiest bend, while at the same timeleaving a hinge with the highest strength and resilience. Score depthsranging between 20% to 50% were tested, with a score depth of 25%yielding the best results. In addition, it was found that thicker sheets(0.4-0.5 mm) gave a better score and yielded a stronger, more rigid clamshell container.

Example 92

A clam shell was made using the sheets of Examples 88, except that atriple reverse hinge was used. That is, a series of three score cutswere cut into the outer side of the claim shell container. Because thisdecreased the distance that each individual score line had to bend, theresulting hinge could be opened and closed more times without breakingcompared to a single score cut hinge.

Example 93

Cold cups made according to Examples 71 and 72 were passed through acommercial wax coating machine, whereby a uniform layer of wax wasapplied to the surface. The layer of wax completely sealed the surfaceof the cup to moisture and rendered it watertight.

Example 94

Cold cups made according to Examples 71 and 72 were coated with anacrylic coating using a fine spraying nozzle. As did the wax in Example93, the layer of acrylic coating completely sealed the surface of thecup to moisture and rendered it watertight. However, the acrylic coatinghad the advantage that it was not as visible as the wax coating. Becausea thinner acrylic coating was possible, the cup looked almost as if itwere uncoated. The glossiness of the cup could be controlled by usingdifferent types of acrylic coatings.

Example 95

Cold cups made according to Examples 71 and 72 were coated with acommercially used melamine coating using a fine spraying nozzle. As inExamples 93 and 94, the layer of melamine coating completely sealed thesurface of the cup moisture and rendered it watertight. However, themelamine coating was also less visible and could be applied in a thinnercoat compared to the wax coating. The glossiness of the cup could becontrolled by using different types melamine coatings.

Example 96

Cold cups made according to Examples 71 and 72 were coated with atotally environmentally sound coating consisting of a mixture ofhydroxymethylcellulose plasticized with polyethylene glycol. Thiscoating completely sealed the surface of the cup to moisture andrendered it watertight. However, the surface looked even more naturaland less glossy as compared to cups coated with wax, acrylic, ormelamine.

Examples 97-100

Clam shell containers made according to Examples 73 and 74 werealternatively coated with the same coating materials used to coat thecold cups in Examples 93-96. The results were substantially identical tothose achieved with the coated cups.

    ______________________________________                                        Example      Coating Material                                                 ______________________________________                                        97           wax                                                              98           acrylic                                                          99           melamine                                                         100          plasticized hydroxymethylcellulose                               ______________________________________                                    

Examples 101-104

French fry containers made according to Examples 75-80 werealternatively coated with the same coating materials used to coat thecold cups in Examples 93-96. The results were substantially identical tothose achieved with the coated cups.

    ______________________________________                                        Example      Coating Material                                                 ______________________________________                                        101          wax                                                              102          acrylic                                                          103          melamine                                                         104          plasticized hydroxymethylcellulose                               ______________________________________                                    

Examples 105-108

Frozen food containers made according to Examples 81-86 werealternatively coated with the same coating materials used to coat thecold cups in Examples 93-96. The results were substantially identical tothose achieved with the coated cups.

    ______________________________________                                        Example      Coating Material                                                 ______________________________________                                        105          wax                                                              106          acrylic                                                          107          melamine                                                         108          plasticized hydroxymethylcellulose                               ______________________________________                                    

Examples 109-112

Cold cereal boxes made according to Example 87 were alternatively coatedwith the same coating materials used to coat the cold cups in Examples93-96. The results were substantially identical to those achieved withthe coated cups.

    ______________________________________                                        Example      Coating Material                                                 ______________________________________                                        109          wax                                                              110          acrylic                                                          111          melamine                                                         112          plasticized hydroxymethylcellulose                               ______________________________________                                    

Examples 113-116

Drinking straws made according to Example 88 are alternatively coatedwith the same coating materials used to coat the cold cups in Examples93-96. The results are substantially identical to those achieved withthe coated cups with regard to the outer surface of the straws, althoughit is more difficult to adequately coat the inside of the straw in thismanner.

    ______________________________________                                        Example      Coating Material                                                 ______________________________________                                        113          wax                                                              114          acrylic                                                          115          melamine                                                         116          plasticized hydroxymethylcellulose                               ______________________________________                                    

Example 117

The same mix design set forth in Examples 71-88 was used to manufacturesheets of varying thickness between 0.,25 mm and 0.5 mm. The mixing,extrusion, and calendering processes were in every way the same. Drysheets of each thickness were cut into circular shapes and formed intopaper plates using a commercial mechanical press fitted with aprogressive die used to make such plates out of paper stock. The detailsof the stamped cementitious plates stood out perfectly and weresubstantially similar in shape, strength and appearance compared toconventional paper plates. However, the cementitious plates were foundto be more rigid than conventional paper plates and, hence, posses morestructural integrity when food is placed on or within the plates.

Example 118

Dry sheets obtained in Example 117 were first wetted contain 5%additional water by weight of the initially dry sheet before they werepressed into plates (keeping in mind that the apparently "dry" sheetscontain water within hydraulically settable structural matrix even whenthey feel dry and posses maximum stiffness). The added water helped thesheets become more flexible (i.e., higher elongation before rupture)which resulted in a plate that had a better impression and detailcompared to conventional paper plates formed by the same process. Thepress was heated to 200° C. and the extra water evaporated during thevery short press time (<1 sec) through vent holes in the heated mold,yielding a dry product of higher stiffness than paper.

Example 119

Dry sheets obtained in Example 117 were first wetted to contain 10%additional water by weight of the initially dry sheet before they werepressed into plates. The added water helped the sheets become even moreflexible, although the impressions and detail were comparable to theresults of Example 118. As a result of adding extra water, the moldingtook a little more time in order to drive off the extra water and form aplate that was substantially dry. It was found that the molding timecould be reduced by increasing the temperature of the mold. The finalproduct was stiffer than comparable paper plates.

Example 120

Dry sheets obtained in Example 117 were first wetted to contain 20%additional water by weight of the initially dry sheet before they werepressed into plates. The added water helped the sheets become even moreflexible than the sheets in Example 119 to the point where the moldingprocess could be classified as a wet sheet molding process rather thandry sheet stamping. The resulting product was superior to a paperstamping process because there were no fold lines whatsoever in thepressed material. The final product was stiffer than comparable paperplates.

Example 121

Dry sheets obtained in Example 117 were first wetted to contain 30%additional water by weight of the initially dry sheet before they werepressed into plates. The added water helped the sheets become slightlymore flexible than the sheets in Example 120, although the moldingprocess and results were similar. The resulting product was superior toa paper stamping process because there were no fold lines whatsoever inthe pressed material. Because of the extra water, the molding processtook a little longer than when less water was used to moisten thesheets. Heating the molds to a higher temperature was found to reducemolding times. The final product was stiffer than comparable paperplates.

Example 122

The processes of Examples 117-121 were repeated in every way except thata commercial acrylic coating was applied to one side of the sheets priorto their being pressed into plates as above. In the case where a sheetwas remoistened, the water was sprayed on the side opposite the sideonto which the coating was placed. The coating provided the plates witha glossier surface and rendered them more water resistant.

Example 123

The processes of Examples 117-121 were repeated in every way except thata commercial polyethylene coating was applied to one side of the sheetsprior to their being pressed into plates as above. In the case where asheet was remoistened, the water was sprayed on the side opposite theside onto which the coating was placed. The coating provided the plateswith a glossier surface and rendered them more water resistant.

Examples 124-130

The processes set forth in Examples 117-123 were repeated except thatthe sheets were pressed into the shape of a bowl using a conventionalpress used to manufacture disposable paper bowls from paper stock. Thecementitious bowls had a diameter of 15 cm and a depth of 3 cm. Becauseof the deeper impression and greater degree of bending and deformationnecessary to form a bowl from a flat sheet, sheets having an addedmoisture content less than 10% yielded some defects. However, the use ofat least 10% added water gave a good product with better impressions, nofolding and a smoother surface compared to bowls made from paper.

    ______________________________________                                        Example      Added Water                                                                              Coating                                               ______________________________________                                        124           0%        none                                                  125           5%        none                                                  126          10%        none                                                  127          20%        none                                                  128          30%        none                                                  129          variable   acrylic                                               130          variable   polyethylene                                          ______________________________________                                    

Examples 131-137

The molding processes set forth in Examples 117-123 were repeated exceptthat the sheets were pressed into the shapes of a two part breakfastplatter, including a top and bottom half. The top half had a length of20 cm and a depth of 3.5 cm, while the bottom half had a length of 21 cmand a depth of 1.0 cm. Sheets having a thickness of 0.8 mm were used,yielding pieces which each weighed between 12-15 g. Although they wereas similar in weight compared to existing breakfast platters used in thefast food industry, they were less flimsy.

The top and bottom halves were complementary in size and could beinterlocked together to form a closed container using tabs on the sidesof the top half and slots in the sides of the bottom half. The productwas flexible enough that nonshattering failure occurred when crushed.Those that were coated exhibited a synergistic effect between thecoating and the hydraulically settable structural matrix, wherein theproduct became stronger, tougher and more elastic before rupture due tothe high elongation of the elastomeric coating.

    ______________________________________                                        Example      Added Water                                                                              Coating                                               ______________________________________                                        131           0%        none                                                  132           5%        none                                                  133          10%        none                                                  134          20%        none                                                  135          30%        none                                                  136          variable   acrylic                                               137          variable   polyethylene                                          ______________________________________                                    

Example 138

A two-part breakfast platter was manufactured using the mix design setforth in Examples 131-137, except that instead of drying and thenrewetting the calendered sheet a wet sheet was directly molded into theshape of the breakfast platter. The wet sheet was readily molded andresulted in very few surface and structural defects. The breakfastplatter made in this example had a thickness of 0.5 mm and possessedsimilar weight and insulation properties as the platter made in theprevious examples.

Example 139

Containers set forth above were placed in a microwave oven and testedfor microwave compatibility; that is, they were tested to determinewhether the containers themselves, or the food items within them, becomehot when container and food were exposed to microwave radiation.Although the containers may have been expected to absorb some of theradiation and become hot in light of the water tied up within thehydraulically settable structural matrix, in fact, the containersthemselves remained cool. Because of the low dielectric constant of thematerial, all of the energy was found to go into the food, not thecontainer.

For the same reason, steam which may have condensed onto the surface ofthe container during initial stages of the microwaving was found toquickly revaporize under further microwaving. Therefore, when the foodcontainer was opened, no condensed steam was found on the surface of thecontainer after the microwave process. Any excess steam comes out whenthe container is opened, leaving food which looks and tastes better.This is in sharp contrast to polystyrene containers, which tend toaccumulate large amounts of condensed steam on the container surfaces,thereby rendering a "soggier," and hence less desirable, food product.In addition, polystyrene containers often melt if the food is heated toolong.

The specific heats of the hydraulically settable materials of thepresent invention are relatively low, being about 0.9 J/g·K and having alow thermal constant within the range of 0.06-014 W/m·K. This allows forless thermal conductance from the food to the container during themicrowave process. It was possible, therefore, to in all cases removethe container from the microwave without burning the hands. After thecontainer was removed from the microwave oven it slowly warmed (byabsorbing some of the heat within the food), but never became too hot totouch.

Example 140

Flat paper-like sheets suitable for manufacturing a wide variety of foodand beverage containers were manufactured from a hydraulically settablemixture containing the following:

    ______________________________________                                        Portland Cement       1.0 kg                                                  Perlite               0.3 kg                                                  Hollow Glass Spheres (<0.1 mm)                                                                      0.8 kg                                                  Mica                  0.5 kg                                                  Fiber (Southern pine) 0.25 kg                                                 Tylose ® FL 15002 0.2 kg                                                  Water                 2.6 kg                                                  ______________________________________                                    

The cement, mica, fiber, Tylose®, and water were mixed together in ahigh shear mixer for 5 minutes, after which the perlite and hollow glassspheres were added and the resulting mixture mixed using low shear. Themixture was extruded using an auger extruder and a die into a sheet 30cm wide and 0.6 cm thick. The sheet was passed successively betweenpairs of heated rollers in order to reduce the thickness of the sheet tobetween 0.1 mm and 2 mm.

As a result of the lower specific surface area of the glass spheres(200-250 m² /kg) compared to perlite, the mixture of Example 140 yieldeda product with a more uniform thickness and improved surface finishcompared to the mix design of Examples 71-88. The reduced specificsurface area of the aggregates reduced the amount of moisture that wasremoved when contacting the heated calendering rollers. The material,therefore, remains more moldable, retains the optimum rheology, andresults in less microdefects and more uniformity during the calenderingprocess.

Example 141

The sheets made according to Example 140 were cut, rolled, and gluedinto 10 oz. drinking cups using a commercial paper cup manufacturingmachine. The cups were alternatively coated with a wax coating in orderto render them more waterproof.

Example 142

The mix design and molding processes of Examples 71-88 were repeated inevery way except that the mica was substituted with 0.5 kg kaolin. Thesheets made using this alternative mix design yielded sheets that had aglossier surface than where mica was used. The glossier surface resultedfrom the alignment of the smaller kaolin particles within the sheetsurface when the sheet was successively passed between a pair ofcalendering rollers, which also acted like a pair of smoothing rollers.

Example 143

The mix design and molding process of Example 142 were repeated in everyway except that 1.0 kg of kaolin was used. The sheets that were moldedusing this increased amount of kaolin had a smoother surface finish thanwhen only 0.5 kg kaolin was used.

Example 144

The mix design and molding process of Example 142 were repeated in everyway except that 1.5 kg of kaolin was used. The sheets that were moldedusing this increased amount of kaolin had a smoother surface finish thanwhen only 0.5 kg or 1.0 kg of kaolin was used. However, the increase inkaolin yielded a more brittle sheet. In addition, drying defects due tothe increased specific surface area were somewhat problematic whenpassing the sheet between the reduction rollers.

Example 145

The mix design and molding processes of Examples 71-88 were repeated inevery way except that the perlite was excluded and the amount of micawas increased to 1.5 kg. The resulting sheets made using thisalternative mix design had a smoother finish. However, the hydraulicallysettable structural matrix was more dense and more brittle. In addition,there was an increase in drying defects. The sheets could be rolled intocups but with minor surface defects in the form of cracks. Also, curlingof the top was less successful than in Examples 71 and 72.

Example 146

The mix design and molding processes of Examples 71-88 were repeated inevery way except that the amount of perlite was increased to 1.0 kg. Theresulting sheets and containers made therefrom had a slightly lowerdensity but also slightly lower strength and toughness.

Example 147

The mix design and molding processes of Examples 71-88 were repeated inevery way except that the amount of perlite was increased to 0.75 kg.The resulting sheets and containers made therefrom had a slightly lowerdensity but also slightly lower strength and toughness. However, thestrength characteristics were somewhat better than when 1.0 kg ofperlite was used, as in Example 146.

Example 148

The mix design and molding processes of Examples 71-88 were repeated inevery way except that the amount of perlite was reduced to 0.25 kg. Theresulting sheets and containers made therefrom had a higher fibercontent and a slightly higher density, but had greater strength andtoughness.

Example 149

The mix design and molding processes of Examples 71-88 were repeated inevery way except that perlite was eliminated from the mix designaltogether. The resulting sheets and containers made therefrom had aslightly higher density, but had greater strength and toughness.

Example 150

An insulating cup was manufactured by directly molding a hydraulicallysettable mixture that contained the following components:

    ______________________________________                                        Portland cement       1.0 kg                                                  Hollow Glass Spheres (<1 mm)                                                                        1.1 kg                                                  Fiber (Southern Pine) 0.08 kg                                                 Tylose ® FL 15002 0.1 kg                                                  Water                 2.5 kg                                                  ______________________________________                                    

The cement, fiber, Tylose® and water were mixed together for 5 minutesusing a high shear mixer. Thereafter, the hollow glass spheres wereadded and the resulting mixture mixed for an additional 5 minutes in alow shear mixer. The resulting mixture had the consistency of adough-like material and could be easily molded while retaining its shapewhile in the green state.

The mixture was molded using a male and female die pair into the shapeof a cup. The mold dies where heated to a temperature of 110°-130° C. toprevent sticking. After demolding the cup was self-supporting in thegreen state. The green cup was allowed to dry.

The cup had a compressive strength of 1.1 MPa, a tensile strength of 0.8MPa, and a k-factor of 0.07 W/m·K.

Example 151

The mix design and molding processes of Example 150 were repeated inevery way, except that the glass spheres were substituted with 1.1 kg ofperlite. The resulting dried molded cup had a compressive strength of8.0 MPa, a tensile strength of 3.2 MPa, and a k-factor of 0.14 W/m·K.Thus, the use of perlite instead of hollow glass spheres yields a cupwith greatly increased tensile and compressive strength, but with ahigher level of thermal conductivity.

Example 152

The mix design and molding processes of Example 150 were repeated inevery way, except that glass spheres having carefully graded diameterswere used in order to increase the particle packing efficiency of thehydraulically settable material. In particular, 231 g of fine, 528 g ofmedium, and 341 g of coarse hollow glass spheres were included, for atotal content of 1.1 kg. The average diameter of the hollow glassspheres designated as "fine" was 30 microns; of the "medium" was 47microns; and of the "coarse" was 67 microns.

The mixture had better workability due to the decrease in interstitialspaces between the particles. The resulting cups had a smoother surfaceand slightly superior strength characteristics. The k-factor was 0.083W/m·K (slightly higher than in Example 150) due to the slight decreasein interstitial space and increase in overall density of the material.

The following examples relate to tests that were performed in order tooptimize the mix designs that would yield products having the preferredperformance criteria. Although only sheets were made in the remainingtest examples, it will be understood to one of ordinary skill in the arthow such sheets could be formed into appropriate food or beveragecontainers using any of the methods (including the examples) set forthwithin the Specification. In addition, many of ::he mix designs couldalso have application in either direct molding or wet sheet molding offood or beverage containers.

Examples 153-158

Cementitious sheets having a thickness of 0.4 mm were manufacturedaccording to the processes set forth in Examples 71-88 from ahydraulically settable mixture containing he following components:

    ______________________________________                                        Portland Cement   1.0 kg                                                      Perlite           variable                                                    Mica              0.5 kg                                                      Tylose ® FL 15002                                                                           0.2 kg                                                      Fiber (Southern pine)                                                                           0.25 kg                                                     Water             variable                                                    ______________________________________                                    

The effect of adding varying amounts of perlite was studied to determinethe effect on the properties of material, particularly the strengthproperties of the hardened sheet. Because of the water-absorbingbehavior of perlite, was necessary to decrease the amount of water asthe amount perlite was decreased in order to maintain the same levelrheology and workability. The amount of perlite and water .±::! of eachexample was as follows:

    ______________________________________                                        Example         Perlite Water                                                 ______________________________________                                        153             0.5 kg  2.15 kg                                               154             0.4 kg  2.05 kg                                               155             0.3 kg  1.85 kg                                               156             0.2 kg  1.65 kg                                               157             0.1 kg  1.50 kg                                               158             0.0 kg  1.40 kg                                               ______________________________________                                    

The extrusion and calendering processes had the effect of longitudinallyorienting the fibers in a substantially unidirectional manner.Therefore, the sheets possessed "strong" and a "weak" direction. Thesheets were tested tensile strength in the two directions, designated as0° for the strong direction and 90° for the weak direction.In addition,for each sheet, the level of elongation before failure was measured aswas Young's modulus of elasticity.

The sheets were also tested for strength in the intermediate, or 45°,direction although only exemplary results for tests in this directionare given. The tensile strength, elongation, and Young's modulus of thesheets in 45° direction generally fell between those measured in thestrong and weak directions, although as a general rule they were closerto the same properties measured in the weak direction. The results areset forth as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (MPa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        153    10.67   5.18    1.57%  0.66%  2297  1375                               154    11.2    5.33    2.38%  1.25%  2156  1559                               155    13.45   6.27    2.22%  1.00%  2956  1548                               156    16.06   7.73    3.05%  1.01%  3006  1674                               157    17.91   10.0    1.38%  0.98%  3375  2605                               158    13.87   6.76    1.03%  0.48%  3058  2434                               ______________________________________                                    

These examples demonstrate that as the amount of perlite was decreased(which increased the concentration of fiber), the tensile strength,elongation, and Young's modulus all increased, except after the amountof perlite was reduced below a certain amount. Both the tensile strengthand Young's modulus continued to increase until the perlite was left outaltogether, as in Example 158. However, the ability of the material toelongate increased as the perlite was decreased, until less than 0.2 kgwas used, after which the elongation dropped considerably. Reducing theamount of perlite beyond a certain point in this mix design results inan increased amount of defects in the sheets, which decreases thestrength, elongation, and elasticity of the sheets.

However, in general, as the amount of perlite is decreased, theconcentrations of fiber, rheology modifying agent, and hydraulic cementare increased, which would be expected to add to the tensile strength.In addition, increasing the concentration of cement would add to thestiffness (modulus) while negatively affecting the elongation ability ofthe product.

Another interesting point is that the ratio of tensile strength in thestrong and weak directions was only about 2::1 in these sheets, whereasin paper products the ratio :us typically 3:1.

While the sheets tested above were substantially dry, sheets madeaccording to Examples 153-158 were further dried in an oven in order toobtain a sheet of maximum dryness. The further drying of the sheets wasperformed in order to portray a more accurate picture of the strengthand other properties of the sheets under constant conditions. Dependingon the mix designs, humidity during the test procedures, or othervariables, the sheets would be expected to absorb or retain a certainamount of moisture. The strength, elongation, and modulus of elasticityresults for the further dried sheets are set forth as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (MPa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        153    14.01   N/A     1.53%  N/A    2559  N/A                                154    13.6    6.23    1.34%  1%     1799  2071                               155    16.81   8.11    1.76%  1.08%  2659  1587                               156    19.32   8.91    1.82%  1.16%  4002  1609                               157    20.25   11.23   1.41%  0.63%  3448  1536                               158    17.5    N/A     0.81%  N/A    3457  N/A                                ______________________________________                                    

As shown by these examples, totally drying the sheets decreases theelongation somewhat, whereas the strength and modulus of elasticity areincreased. These examples therefore teach that where increased strengthand stiffness are important, the sheet should be totally dry. Whereincreased elongation is important, the elongation may be controlled withthe humidity of the sheet.

Examples 159-163

Cementitious sheets having a thickness of 0.4 mm were manufacturedaccording to the processes set forth in Examples 71-88 from ahydraulically settable mixture containing the following components:

    ______________________________________                                        Portland Cement    1.0 kg                                                     CaCO.sub.3 (chalk)                                                                              variable                                                    Tylose ® FL 15002                                                                           0.20 kg                                                     Fiber (Southern pine)                                                                           0.25 kg                                                     Water             variable                                                    ______________________________________                                    

The effect of adding varying amounts of chalk was studied to determinethe effect on the properties of the material, particular the strengthproperties of the hardened sheet. Because of the reduced water-absorbingbehavior of chalk compared to perlite, it was not necessary to decreasethe amount of water by the same level as the amount of chalk wasdecreased in order to maintain the same level of rheology andworkability. The amount of CaCO₃ and water for each example was asfollows:

    ______________________________________                                        Example         CaCO.sub.3                                                                            Water                                                 ______________________________________                                        159             5.0 kg  2.25 kg                                               160             4.0 kg  2.15 kg                                               161             3.0 kg  2.05 kg                                               162             2.0 kg  2.00 kg                                               163             1.0 kg  1.96 kg                                               ______________________________________                                    

The strength, elongation, and Young's modulus of each of the totally drysheets formed from the different mix designs are set forth as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (MPa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        159    11.59   N/A     N/A    N/A    N/A   NIA                                160    16.16   N/A     0.72%  N/A    4638  N/A                                161    14.82   5.22    0.97%  0.42%  4521  3521                               162    20.43   8.26    1.11%  0.56%  4301  2773                               163    18.43   7.98    1.13%  0.51%  3902  3320                               ______________________________________                                    

The use of chalk yields sheets with a smoother, more defect-free surfaceas well as a more homogeneous microstructure compared to where perliteis used.

Examples 164-170

Cementitious sheets having a thickness of 0.4 mm were manufacturedaccording to the processes set forth in Examples 77-88 from ahydraulically settable mixture containing the following components:

    ______________________________________                                        Portland Cement   1.0 kg                                                      Perlite           0.5 kg                                                      Mica              0.5 kg                                                      Tylose ® FL 15002                                                                           variable                                                    Fiber (Southern pine)                                                                           0.25 kg                                                     Water             variable                                                    ______________________________________                                    

The level of Tylose® was altered in order to determine the effect ofincreasing amounts of Tylose® within the cementitious mixture.Increasing the amount of Tylose® within the mixture required theaddition of more water in order to dissolve the Tylose® and maintainsimilar rheology and workability.

    ______________________________________                                        Example         Tylose ®                                                                           Water                                                ______________________________________                                        164             0.1 kg   2.25 kg                                              165             0.3 kg   2.75 kg                                              166             0.4 kg   3.00 kg                                              167             0.5 kg   3.25 kg                                              168             0.6 kg   3.50 kg                                              169             0.7 kg   3.75 kg                                              170             0.8 kg    4.0 kg                                              ______________________________________                                    

The tensile strength and elongation properties increased up to a pointas more Tylose® was added, while the Young's modulus fluctuated. Theresults of testing oven dried sheets made using the various mix designsare as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (Mpa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        164    N/A     N/A     N/A    N/A    N/A   N/A                                165    13.84   7.25    1.41%  0.75%  2954  1692                               166    16.43   7.9     1.9%   0.83%  2400  2075                               167    21.31   11.58   3.64%  1.06%  3347  2370                               168    16.11   10.35   1.84%  1.13%  2816  1797                               169    15.73   9.56    1.81%  0.93%  2690  1851                               170    18.86   10.33   2.35%  1.45%  2790  1570                               ______________________________________                                    

As illustrated, increasing the concentration of Tylose® will generallytend to increase the tensile strength, modulus, and elongation beforerupture. A higher elongation ability could be expected to aid in curlingthe rim of a cup formed from a sheet, while increasing the strength ofthe sheet at a score cut. However, as the concentration of Tylose® isincreased above a certain amount, the material becomes less workable andmore defects are introduced within the structural matrix, which would beexpected to reduce the strength, modulus, and elongation of the sheet.Nevertheless, the amount of defects (and resulting strength properties)can be improved by optimizing the calendering process.

Example 171

Based on the understanding that tensile strength and elongationgenerally increase as both the amount of fiber and Tylose® are increasedwithin a mix design, a mix design was made which maximized both. Thecementitious mixture included the following components:

    ______________________________________                                        Portland cement   1.0 kg                                                      Water             2.2 kg                                                      Perlite           0.1 kg                                                      Fiber (Southern pine)                                                                           0.25 kg                                                     Tylose ® FL 15002                                                                           0.5 kg                                                      ______________________________________                                    

The mixture was extruded and then passed between a series of pairs ofrollers into a sheet having a thickness of 0.4 mm. The totally driedsheet was found to have superior strength and elongation properties. Thetensile strength was tested as 39.05 MPa in the strong direction and18.86 MPa in the weak direction; the elongation was 1.97% in the strongdirection and 1.23% in the weak direction; and the modulus of elasticitywas 3935 in the strong direction and 2297 in the weak direction, whichis comparable to normal paper.

Examples 172-176

Cementitious sheets having a thickness of 0.4 mm were manufacturedaccording to the processes set forth in Examples 71-88 from ahydraulically settable mixture containing the following components:

    ______________________________________                                        Portland Cement      1.0 kg                                                   Hollow glass spheres (4000 psi)                                                                    variable                                                 Tylose ® FL 15002                                                                              0.2 kg                                                   Fiber (Southern pine)                                                                              0.25 kg                                                  Water                variable                                                 ______________________________________                                    

The effect of adding varying amounts of hollow glass spheres was studiedto determine the effect on the properties of the material, particularlythe strength properties of hardened sheet. Although glass spheres do notabsorb large amounts of water, less water was required to maintain thesame rheology as the amount of glass spheres was decreased because ofthe corresponding decrease in interpartculate space. The amounts ofglass spheres and water for each example are as follows:

    ______________________________________                                        Example        Glass Spheres                                                                            Water                                               ______________________________________                                        172            0.5 kg      1.6 kg                                             173            0.4 kg     1.45 kg                                             174            0.3 kg     1.40 kg                                             175            0.2 kg     1.35 kg                                             176            0.1 kg     1.25 kg                                             ______________________________________                                    

The strength, elongation, and Young's modulus of each of the totally drysheets formed from the different mix designs are set forth as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (MPa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        172    10.34   3.69    2.2%   1.52%  1166  620                                173    11.1    4.79    2.02%  1.49%  1446  677                                174    12.38   5.71    1.58%  1.15%  1800  870                                175    14.52   6.89    1.5%   1.1%   1935  1220                               176    19.45   9.66    1.54%  0.96%  2660  1741                               ______________________________________                                    

As seen with glass spheres, the modulus of elasticity is much lowerwhile the elongation is fairly high compared to other mix designs. Thesheets are therefore more pliable and elastic. The sheets formed inExamples 172-176 were highly thermally insulating, with k-factorsranging from 0.08-0.14 W/m·K.

Examples 177-180

Cementitious sheets having a thickness of 0.4 mm were manufacturedaccording to the process set forth in Examples 71-88 from ahydraulically settable mixture containing the following components:

    ______________________________________                                        Portland Cement   1.0 kg                                                      Perlite           0.5 kg                                                      Mica              variable                                                    Tylose ® FL 15002                                                                           0.2 kg                                                      Fiber (Southern pine)                                                                           0.25 kg                                                     Water             variable                                                    ______________________________________                                    

The effect of adding varying amounts of mica was studied to determinethe effect on the properties of the material, particularly the strengthproperties of the hardened sheet. Because of the water-absorbingbehavior of mica, was necessary to increase the amount of water as theamount mica was increased in order to maintain the same level rheologyand workability. The amounts of mica and water within each example areas follows:

    ______________________________________                                        Example         Mica    Water                                                 ______________________________________                                        177             1.0 kg  2.7 kg                                                178             1.5 kg  2.9 kg                                                179             2.0 kg  3.0 kg                                                180             2.5 kg  3.2 kg                                                ______________________________________                                    

The strength, elongation, and Young's modulus of each of the totally drysheets formed from the different mix designs are set forth as follows:

    ______________________________________                                        Strength (MPa) Elongation (ΔL/L)                                                                     Modulus (MPa)                                    Example                                                                              0°                                                                             90°                                                                            0°                                                                            90°                                                                           0°                                                                           90°                         ______________________________________                                        177    9.92    4.61     0.825%                                                                              0.652% 2127  1257                               178    9.37    5.3     0.71%  0.49%  3079  2188                               179    11.14   4.05    0.79%  0.314% 3100  1520                               180    11.41   4.76    0.58%  0.32%  2693  1282                               ______________________________________                                    

Increasing the concentration of mica increases the strength of thesheets while reducing their elongation ability. Sheets containing largeramounts of mica became very brittle.

Example 181

Using any of the mix designs set forth above, a hydraulically settablemixture is made by substituting gypsum hemihydrate for the hydrauliccement in roughly the same quantity by weight. The hydraulicallysettable mixture will have a faster setting time but will generallyresult in sheets having similar strength, elongation, and stiffnessproperties.

Example 182

Using any of the mix designs set forth above, a hydraulically settablemixture is made by substituting calcium oxide for the hydraulic cement.The hydraulically settable mixture will have a slower setting time dueto the slower reaction between calcium oxide and carbon dioxide, butwill generally result in sheets having similar strength, elongation, andstiffness properties. However, by removing much of the water within themixture during or after the molding process, a level of quickly attainedgreen strength will be possible.

Example 183

A hydraulically settable mixture is made having the followingcomponents:

    ______________________________________                                        Gypsum hemihydrate                                                                              1.0 kg                                                      Perlite           0.5 kg                                                      Tylose ®      0.075 kg                                                    Fiber             0.25 kg                                                     Water             2.6 kg                                                      ______________________________________                                    

The gypsum, Tylose®, fiber, and water are mixed together in a high shearmixer for 3 minutes, after which the perlite is added and mixed in a lowshear mixer for an additional 3 minutes.

The mixture is extruded into a sheet having a thickness of 6 mm and thencalendered in steps in order to reduce the thickness of the sheets to afinal thickness ranging between 0.25 mm to 0.5 mm.

These sheets are readily formed into an appropriate food or beveragecontainer using any appropriate procedure set forth in thisSpecification. The strength properties are comparable to containers madeusing hydraulic cement and may be useful in the place of, e.g., paper,cardboard, or polystyrene containers.

Example 184

Any of the cementitious mix designs using hydraulic cement is altered toinclude about 25% gypsum hemihydrate by weight of the hydraulic cement.The gypsum acts as a water absorbing component (or internal dryingagent) and results in quicker form stability. The strength properties ofcontainers formed therefrom are comparable to mixtures not includinggypsum.

Example 185

A set accelerator is included within any of the above mix designs,resulting in a hydraulically settable mixture that will more quicklyachieve form stability. The final strength of the material will becomparable to materials in which a set accelerator is not used.

Example 186

Waste cementitious containers were composted along with waste food.After 4 weeks, the containers were completely broken down and resultedin good compost.

IV. Summary

From the foregoing, it will be appreciated that the present inventionprovides novel compositions and processes for hydraulically settablecontainers for the storage, dispensing, packing, and portioning of foodand beverages.

The present invention also provides novel compositions and processes forhydraulically settable containers which have insulating and otherproperties comparable to that of polystyrene foam containers, but whichare more environmentally neutral. Specifically, the present inventiondoes not require the use of, or emit, chemicals which have beenimplicated as causing depletion of the ozone layer, nor does it createunsightly garbage which does not degrade, or which only very slowlydegrades over time in landfills.

In addition, the present invention also provides novel compositions andprocesses for hydraulically settable containers which can be massproduced at relatively low cost.

Further, the present invention provides novel positions and processesfor hydraulically settable containers which are flexible and disposable,but which are much more environmentally sound in their disposal thanother disposable containers, such as paper, plastic, polystyrene foam,and metal materials. The present invention provides novel compositionsand processes for hydraulically settable containers which areessentially comprised of the same compounds as the earth, and aresimilar to dirt and rock, and therefore pose little or no risk to theenvironment when discarded.

The present invention further provides novel compositions and processesfor which the raw materials may be obtained from the earth, eliminatingthe need to cut down large numbers of trees in order to create thestarting raw materials, as is required for the manufacture of papercontainers.

The present invention further provides novel compositions and processesfor improving the safety of storage and dispensing containers, in thathydraulically settable containers do not release harmful chemicals likedioxin into the foodstuffs therein, nor are dioxins produced during themanufacture of such containers.

The present invention further provides novel compositions and processesfor improving the recyclability of disposable containers, particularlysince the hydraulically settable materials can be reintroduced into newcement paste as an aggregate, or be incorporated as a suitable aggregatein many cement applications.

The present invention further provides novel compositions and processesfor achieving lightweight containers which still give sufficientstructural support for the food or beverage product.

The present invention further provides novel hydraulically settable foodand beverage containers which will maintain their shape without externalsupport, even while in the green state immediately after molding, andrapidly achieve sufficient strength so that the molded containers can behandled using ordinary manufacturing methods.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects as illustrative onlyand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. An article of manufacture comprising a food or beverage container formed from a hydraulically settable matrix, said matrix including the chemical reaction product of a hydraulically settable mixture comprising a hydraulically settable binder selected from the group consisting of portland cement, slag cement, calcium aluminate cement, silicate cement, phosphate cement, high-alumina cement, and magnesium oxychloride cement, water, and a rheology-modifying agent, the hydraulically settable mixture having a rheology and early green strength during formation of the food or beverage container such that the hydraulically settable matrix of the container is form stable through the removal of water from the hydraulically settable mixture within a period of time less than about 10 minutes after being positioned into a desired shape of the food or beverage container, the hydraulically settable matrix having a density less than about 1.5 g/cm³, said hydraulically settable matrix having a thickness of less than about 5 mm.
 2. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 5 minutes after being positioned into the desired shape.
 3. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about one minute after being positioned into the desired shade.
 4. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 10 seconds after being positioned into the desired shape.
 5. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about three seconds after being positioned into the desired shape.
 6. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the food beverage container has a tensile strength to bulk density ratio in the range from about 1 MPa·cm³ /g to about 300 MPa·cm³ /g.
 7. An article of manufacture as defined in claim 1, wherein the matrix of the hydraulically settable food beverage container has a tensile strength to bulk density ratio in the range from about 2 MPa·cm³ /g to about MPa·cm³ /g.
 8. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the food or beverage container has a tensile strength to bulk density ratio in the range from about 3 MPa·cm³ /g about 20 MPa·cm³ /g.
 9. An article of manufacture as defined in claim 1, wherein the hydraulic settable binder includes portland cement.
 10. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has an initial water to hydraulic settable binder ratio in the range from about 0.2 to about
 10. 11. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has an initial water to hydraulic settable binder ratio in the range from about 0.3 to about
 4. 12. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has an initial water to hydraulic cement ratio in the range of from about 0.5 to about 1.5.
 13. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix further comprises at least one aggregate material.
 14. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix of the food or beverage container further comprises a plurality of different types of aggregate materials.
 15. An article of manufacture as defined in claim 13, wherein the aggregate material includes perlite.
 16. An article of manufacture as defined in claim 13, wherein the aggregate material includes hollow glass spheres.
 17. An article of manufacture as defined in claim 13, wherein the aggregates in the hydraulically sortable matrix comprise a plurality of effective diameters and are selected to maximize the particle packing efficiency of the aggregates.
 18. An article of manufacture as defined in claim 13, wherein the aggregate material includes a naturally occurring aggregate which naturally has, or has been treated to create air voids to increase its volume to mass ratio.
 19. An article of manufacture as defined in claim 13, wherein at least a portion of the aggregate material is selected from the group consisting of glass beads, microspheres, calcium carbonate, metals, polymers, ceramic, alumina, and cork.
 20. An article of manufacture as defined in claim 13, wherein said aggregate material imparts a predetermined texture to the hydraulically settable matrix of the food or beverage container.
 21. An article of manufacture as defined in claim 13, wherein the aggregate material includes a material selected from the group consisting of sand, gravel, rock, limestone, sandstone, pumice, vermiculite, and expanded clays.
 22. An article of manufacture as defined in claim 13, wherein the aggregate material includes a material selected from the group consisting of seeds, starches, gelatins, and agar-type materials.
 23. An article of manufacture as defined in claim 13, wherein the matrix has a thickness and wherein the individual particles forming the aggregate material have an average effective diameter in the range from about 1/1000 to about 1/2 of the thickness of the matrix.
 24. An article of manufacture as defined in claim 13, wherein the matrix has a thickness and wherein the individual particles forming the aggregate material have an average effective diameter about 1/1000 to about 1/10 of the thickness of the matrix.
 25. An article of manufacture as defined in claim 13, wherein the matrix has a thickness and wherein the individual particles forming the aggregate material have an average effective diameter less than about 1/100 of the thickness of the matrix.
 26. An article of manufacture as defined in claim 13, wherein the aggregate material imparts a predetermined color to the hydraulically settable matrix of the food or beverage container.
 27. An article of manufacture as defined in claim 13, wherein the aggregate material imparts a predetermined sheen to the hydraulically settable matrix of the food or beverage container.
 28. An article of manufacture as defined in claim 13, wherein the aggregate material imparts a predetermined texture to the hydraulically settable matrix of the food or beverage container.
 29. An article of manufacture as defined in claim 13, wherein the aggregate material is included in an amount in the range up to about 80% by weight of the hydraulically settable mixture.
 30. An article of manufacture as defined in claim 13, wherein the aggregate material is included in an amount in the range from about 3% to about 50% by weight of the hydraulically settable mixture.
 31. An article of manufacture as defined in claim 13, wherein the aggregate material is included in an amount in the range from about 20% to about 35% by weight of the hydraulically settable mixture.
 32. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix further includes fibers which add tensile strength to the hydraulically settable matrix.
 33. An article of manufacture as defined in claim 32, wherein the fibers comprise a plurality of different fibrous materials.
 34. An article of manufacture as defined in claim 32, wherein the fibers comprise a cellulosic material.
 35. An article of manufacture as defined in claim 32, wherein the fibers comprise a material selected from the group consisting of glass, metal, ceramic, boron, carbon, and silica.
 36. An article of manufacture as defined in claim 32, wherein the fibers comprise a material selected from the group consisting of hemp, cotton, bagasse, and abaca.
 37. An article of manufacture as defined in claim 32, wherein the fibers are derived from wood pulp.
 38. An article of manufacture as defined in claim 32, wherein the fibers comprise southern pine.
 39. An article of manufacture as defined in claim 32, wherein the fibers having an average aspect ratio of at least 10:1.
 40. An article of manufacture as defined in claim 32, wherein the fibers having an average aspect ratio of am least 100:1.
 41. An article of manufacture as defined in claim 32, wherein the fibers have an average aspect ratio of at least 500:1.
 42. An article of manufacture as defined in claim 32, wherein the fibers have an average length that is at least twice the average effective diameter of the individual particles of hydraulically settable binder.
 43. An article of manufacture as defined in claim 32, wherein the fibers have an average length that is at least 10 times the average effective diameter of the individual particles of hydraulically settable binder.
 44. An article of manufacture as defined in claim 32, wherein the fibers have an average length that is at least 100 times the average effective diameter of the individual particles of hydraulically settable binder.
 45. An article of manufacture as defined in claim 32, wherein the fibers have an average length that is at lease 1000 times the effective average diameter of the individual particles of hydraulically settable binder.
 46. An article of manufacture as defined in claim 32, wherein the fibers increase the insulative properties of the hydraulically settable matrix.
 47. An article of manufacture as defined in claim 32, wherein the fibers are included in an amount within the range from between about 0.2% to about 50% by volume of the hydraulically settable matrix.
 48. An article of manufacture as defined in claim 32, wherein the fibers are included in an amount within the range from between about 1% to about 30% by volume of the hydraulically settable matrix.
 49. An article of manufacture as defined in claim 32, wherein the fibers are included in an amount within the range from between about 5% to about 15% by volume of the hydraulically settable matrix.
 50. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises a cellulose-based material.
 51. An article of manufacture as defined in claim 50, wherein the cellulose-based material is selected from the group consisting of hydroxymethylethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxyethylpropylcellulose, and mixtures thereof.
 52. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent is selected from the group consisting of alginic acid, phycocolloids, agar, gum arabic, guar gum, locust bean gum, gum karaya, gum tragacanth, and mixtures thereof.
 53. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises a starch-based material.
 54. An article of manufacture as defined in claim 53, wherein the starch-based rheology-modifying agent comprises a material selected from the group consisting of amylopectin, amylose, seagel, starch acetates, starch hydroxyethylethers, ionic starches, long-chain alkylstarches, dextrins, amine starches, phosphates starches, dialdehyde starches, and mixtures thereof.
 55. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises a protein-based material.
 56. An article of manufacture as defined in claim 55, wherein the protein-based rheology-modifying agent comprises a material selected from the group consisting of a prolamine, collagen, gelatin, casein, and mixtures thereof.
 57. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises polylactic acid.
 58. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises a synthetic organic material.
 59. An article of manufacture as defined in claim 58, wherein the synthetic organic-based rheology-modifying agent comprises a material selected from the group consisting of polyvinyl pyrrolidone, polyethylene glycol, polyvinyl alcohol, polyvinylmethyl ether, polyacrylic acids, polyacrylic acid salts, polyvinyl acrylic acids, polyvinyl acrylic acid salts, polyacrylimides, ethylene oxide polymers, latex, synthetic clay, and mixtures thereof.
 60. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent has a concentration up to about 50% by weight of the green hydraulically settable mixture.
 61. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent has a concentration in the range from about 0.2% to about 20% by weight of the green hydraulically settable mixture.
 62. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent has a concentration in the range from about 0.3% to about 3% by weight of the green hydraulically settable mixture.
 63. An article of manufacture as defined in claim 1, wherein the rheology-modifying agent comprises a plurality of different rheology-modifying agents.
 64. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix further comprises a discontinuous, nonagglomerated phase including finely dispersed voids.
 65. An article of manufacture as defined in claim 64, wherein a high shear mixer is used to introduce air voids into the hydraulically settable matrix.
 66. An article of manufacture as defined in claim 65, wherein the hydraulically settable matrix further comprises a stabilizing agent for maintaining the air voids introduced within the hydraulically settable matrix by the high shear mixer.
 67. An article of manufacture as defined in claim 66, wherein the rheology-modifying agent acts as a stabilizing agent.
 68. An article of manufacture as defined in claim 65, wherein the hydraulically settable matrix further comprises an air-entraining agent for incorporating the voids within the hydraulically settable matrix in conjunction with the high shear mixer.
 69. An article of manufacture as defined in claim 68, wherein the air-entraining agent is a surfactant.
 70. An article of manufacture as defined in claim 68, wherein the air-entraining agent is selected from the group consisting of a polypeptide, alkylene, polyol, a synthetic liquid anionic biodegradable solution, and mixtures thereof.
 71. An article of manufacture as defined in claim 68, wherein the air-entraining agent comprises vinsol resin.
 72. An article of manufacture as defined in claim 68, wherein the hydraulically settable matrix further comprises a blowing agent such that when the hydraulically settable matrix is heated, finely dispersed voids are incorporated into the matrix.
 73. An article of manufacture as defined in claim 64, further comprising a material which reacts with the components in the hydraulically settable matrix to produce a gas in order to incorporate voids into the hydraulically settable
 74. An article of manufacture as defined in claim 73, wherein the gas-producing agent is a metal.
 75. An article of manufacture as defined in claim 73, wherein the gas-producing agent is aluminum.
 76. An article of manufacture as defined in claim 73, further comprising a base which accelerates the reaction of the gas-producing agent.
 77. An article of manufacture as defined in claim 76, wherein the base is sodium hydroxide.
 78. An article of manufacture as defined in claim 64, wherein the hydraulically settable matrix has sufficient strength and insulative properties such that a cup formed thereform is capable of maintaining beverages at a temperature greater than approximately 65° C. for at least 10 minutes.
 79. An article of manufacture as defined in claim 64, wherein the hydraulically settable matrix has sufficient strength and insulative properties such that a cup formed therefrom is capable of maintaining beverages at a temperature less than approximately 15° C. for at least 10 minutes.
 80. An article of manufacture as defined in claim 1, wherein the container is in the shape of a drinking cup.
 81. An article of manufacture as defined in claim 80, wherein the hydraulically settable matrix of the drinking cup has sufficient strength and insulative properties to be capable of use in serving beverages at a temperature greater than approximately 65° C.
 82. An article of manufacture as defined in claim 80, wherein the hydraulically settable matrix of the drinking cup has sufficient strength and insulative properties to be capable of use in serving beverages at a temperature less than approximately 15° C.
 83. An article of manufacture as defined in claim 80, wherein the drinking cup is manufactured for a single service use.
 84. An article of manufacture as defined in claim 1, wherein the container is in the shape of a box for the dispensing of food products.
 85. An article of manufacture as defined in claim 84, wherein the hydraulically settable matrix of the box has sufficient strength and insulative properties to be capable of use in serving food products at a temperature less than approximately 0° C.
 86. An article of manufacture as defined in claim 84, wherein the hydraulically settable matrix of the box has sufficient strength and insulative properties to be capable of use in serving food products at a temperature greater than approximately 25° C.
 87. An article of manufacture as defined in claim 84, wherein the box is disposable.
 88. An article of manufacture as defined in claim 84, wherein the container is in the shape of a hingedly closable box.
 89. An article of manufacture as defined in claim 1, wherein the container is in the shape of a straw through which liquid can pass.
 90. An article of manufacture as defined in claim 1, wherein the container is in the shape of a lid of a container.
 91. An article of manufacture as defined in claim 1, wherein the container is in the shape of an egg carton.
 92. An article of manufacture as defined in claim 1, wherein the container is in the shape of a plate.
 93. An article of manufacture as defined in claim 1, wherein the container is in the shape of an article selected from the group consisting of a cup, jar, bottle, carton, case, "clam shell," crate, bowl, tray, and dish.
 94. An article of manufacture as defined in claim 1, wherein the container is in the shape of utensils.
 95. An article of manufacture as defined in claim 2, wherein the weight of the food or beverage container is less than 1/2 of the weight of the food or beverage product that it is designed to contain based upon volume.
 96. An article of manufacture as defined in claim 2, wherein the weight of the food or beverage container is less than 1/4 of the weight of the food or beverage product that it is designed to contain based upon volume.
 97. An article of manufacture as defined in claim 2, wherein the weight of the food or beverage container is less than 1/10 of the weight of the food or beverage product that it is designed to contain based upon volume.
 98. An article of manufacture as defined in claim 64, wherein the hydraulically settable matrix is a lightweight product.
 99. An article of manufacture as defined in claim 80, wherein the hydraulically settable matrix is a lightweight product.
 100. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix is a high density product.
 101. An article of manufacture as defined in claim 13, wherein the hydraulically settable matrix is a high density product.
 102. An article of manufacture as defined in claim 32, wherein the hydraulically settable matrix is a high density product.
 103. An article of manufacture as defined in claim 80, wherein the hydraulically settable matrix is a high density product.
 104. An article of manufacture as defined in claim 84, wherein the hydraulically settable matrix is a high density product.
 105. An article of manufacture as defined in claim 104, wherein the thickness of the hydraulically settable matrix is less than about 2 mm.
 106. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix is sheet product.
 107. An article of manufacture as defined in claim 13, wherein the hydraulically settable matrix is a "sheet-product".
 108. An article of manufacture as defined in claim 32, wherein the hydraulically settable matrix is a "sheet-product".
 109. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has a thickness less than about 1 mm.
 110. An article of manufacture as defined in claim 1, wherein the theology-modifying agent comprises methylhydroxyethylcellulose.
 111. An article of manufacture as defined in claim 1, wherein the theology-modifying agent comprises carboxymethylcellulose.
 112. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has a density less than about 1 g/cm³.
 113. An article of manufacture as defined in claim 1, wherein the hydraulically settable matrix has a density in the range from about 0.1 g/cm³ to about 0.7 g/cm³.
 114. An article of manufacture comprising a food or beverage container formed from a hydraulically settable matrix, said matrix including the chemical reaction products of a hydraulically settable mixture comprising a hydraulically settable binder selected from the group consisting of portland cement, slag cement, calcium aluminate cement, silicate cement, phosphate cement, high-alumina cement, and magnesium oxychloride cement, water, a rheology-modifying agent, and an aggregate material having a concentration relative to each other such that the hydraulically settable mixture has a rheology and early green strength during formation of the food or beverage container such that the hydraulically settable matrix of the container is form stable within a period of time less than about 10 minutes after being positioned into a desired shape of the food or beverage container, the hydraulically settable matrix having a density less than about 1.6 g/cm³, said hydraulically settable matrix having a thickness of less than about 5 mm.
 115. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix has a density less than about 1.5 g/cm³.
 116. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix has a density less than about 1 g/cm³.
 117. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix has a density in the range from about 0.1 g/cm³ to about 0.7 g/cm³.
 118. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 5 minutes after being positioned into the desired shape.
 119. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 1 minute after being positioned into the desired shape.
 120. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix has a thickness less than about 3 mm.
 121. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix has a thickness less than about 1 mm.
 122. An article of manufacture as defined in claim 114, wherein the rheology-modifying agent comprises a cellulose-based material.
 123. An article of manufacture as defined in claim 122, wherein the cellulose-based material comprises a cellulosic ether.
 124. An article of manufacture as defined in claim 122, wherein the cellulose-based material comprises methylhydroxyethylcellulose.
 125. An article of manufacture as defined in claim 122, wherein the cellulose-based material comprises carboxymethylcellulose.
 126. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix further comprises fibers which add tensile strength to the hydraulically settable matrix.
 127. An article of manufacture as defined in claim 114, wherein the hydraulically settable matrix further comprises a discontinuous, nonagglomerated phase including finely dispersed voids.
 128. An article of manufacture as defined in claim 114, wherein the container is in the shape of a drinking cup.
 129. An article of manufacture as defined in claim 114, wherein the container is in the shape of a box.
 130. An article of manufacture as defined in claim 114, wherein the container is in the shape of a plate.
 131. An article of manufacture as defined in claim 114, wherein the food or beverage container is manufactured for a single service use.
 132. An article of manufacture comprising a food or beverage container formed from a hydraulically settable matrix, said matrix including the chemical reaction products of a hydraulically settable mixture comprising a hydraulically settable binder selected from the group consisting of portland cement, calcium aluminate cement, silicate cementer, phosphate cement, high-alumina cement, and magnesium oxychloride cement, water, and a rheology-modifying agent, the hydraulically settable binder being in a concentration in a range from about to about 90% by weight of the hydraulically settable mixture, the hydraulically settable mixture having a rheology and early green strength during formation of the food or beverage container such that the hydraulically settable matrix of the container made therefrom is form stable through the removal of water from the hydraulically settable mixture within a period of time less than about ten minutes after being positioned into a desired shape of the food or beverage container, the hydraulically settable matrix having a density less than about 1.6 g/cm³, said hydraulically settable matrix having a thickness of less than about 5 mm.
 133. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix has a density less than about 1.5 g/cm³.
 134. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix has a density less than about 1 g/cm³.
 135. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix has a density in the range from about 0.1 g/cm³ to about 0.7 g/cm³.
 136. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 5 minutes after being positioned into the desired shape.
 137. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 1 minute after being positioned into the desired shape.
 138. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix has a thickness less than about 3 mm.
 139. An article of manufacture as defined in claim 132, wherein the hydraulically settable matrix has a thickness less than about 1 mm.
 140. An article of manufacture as defined in claim 132, wherein the hydraulically settable binder comprises portland cement.
 141. An article of manufacture as defined in claim 132, wherein the hydraulically settable mixture further includes an aggregate material.
 142. An article of manufacture as defined in claim 132, wherein the hydraulically settable mixture further includes a fibrous material.
 143. An article of manufacture as defined in claim 132, wherein the rheology-modifying agent comprises a cellulose-based material.
 144. The article of manufacture as defined in claim 132, wherein the food and beverage container is manufactured single service use.
 145. An article of manufacture comprising a food or beverage container formed from a hydraulically settable matrix, said matrix including the chemical reaction products of a hydraulically settable mixture comprising a hydraulically settable binder selected from the group consisting of portland cement, slag cement, calcium aluminate cement, silicate cement, phosphate cement, high-alumina cement, and magnesium oxychloride cement, water, a rheology-modifying agent, and a fibrous material, the hydraulically settable mixture having a theology and early green strength during formation of the food or beverage container such that the hydraulically settable matrix of the container is form stable through the removal of water from the hydraulically settable mixture within a period of time less than about 10 minutes after being positioned into a desired shape of the food and beverage container, the hydraulically settable matrix having a density less than about 1.5 g/cm³, said hydraulically settable matrix having a thickness of less than about 5 mm.
 146. An article of manufacture as defined in claim 145, wherein the hydraulically settable matrix has a density less than about 1 g/cm³.
 147. An article of manufacture as defined in claim 145, wherein the hydraulically settable matrix has a density in the range from about 0.1 g/cm³ to about 0.7 g/cm³.
 148. An article of manufacture as defined in claim 145, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 5 minutes after being positioned into the desired shape.
 149. An article of manufacture as defined in claim 145, wherein the hydraulically sortable matrix of the con{airier is form stable within a period of time less than about 1 minute after being positioned into the desired shape.
 150. An article of manufacture as defined in claim 145, wherein the hydraulically sortable matrix has a thickness less than about 3 mm.
 151. An article of manufacture as defined in claim 145, wherein the hydraulically settable matrix has a thickness less than about 1 mm.
 152. An article of manufacture as defined in claim 145, wherein the fibrous material has a concentration in a range from about 0.2% to about 50% by volume of the hydraulically settable matrix.
 153. An article of manufacture as defined in claim 145, wherein the fibrous material has a concentration in a range from about 1% to about 30% by volume of the hydraulically settable matrix.
 154. An article of manufacture as defined in claim 145, wherein the fibrous material has a concentration in from about 5% to about 15% by volume of the hydraulically settable matrix.
 155. An article of manufacture as defined in claim 145, wherein the fibrous material comprises a material selected from the group consisting of hemp, cotton, bagasses, and abaca.
 156. An article of manufacture as defined in claim 145, wherein the fibrous material comprises southern pine.
 157. An article of manufacture as defined in clam 145, wherein the hydraulically settable mixture further includes an aggregate material.
 158. An article of manufacture as defined in claim 145, wherein in the food or beverage container is manufactured for single service use.
 159. An article of manufacture comprising a food or beverage container formed from a hydraulically settable matrix, said matrix including the chemical reaction products of a hydraulically settable mixture comprising a hydraulically settable binder selected from the group consisting of portland cement, slag cement, calcium aluminate cement, silicate cement, phosphate cement, high-alumina cement, and magnesium oxychloride cement, water, and a rheology-modifying agent, the hydraulically settable mixture having a rheology and early green strength during formation of the food or beverage container such that the hydraulically settable matrix of the container formed therefrom is form stable through the removal of water from the hydraulically settable mixture within a period of time less than about 10 minutes after being positioned into a desired shape of the food or beverage container, the hydraulically settable matrix having a density less than about 1.6 g/cm³, said hydraulically settable matrix having a thickness of less than about 3 mm.
 160. An article of manufacture as defined in claim 154, wherein the hydraulically settable matrix has a thickness than about 1 mm.
 161. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix has a thickness less than about 0.5 mm.
 162. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix has a density less than about 1.5 g/cm³.
 163. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix has a density less than about 1 g/cm³.
 164. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix has a density in the range from about 0.1 g/cm³ to about 0.7 g/cm³.
 165. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 5 minutes after being positioned into the desired shape.
 166. An article of manufacture as defined in claim 159, wherein the hydraulically settable matrix of the container is form stable within a period of time less than about 1 minute after being positioned into the desired shape.
 167. An article of manufacture defined in claim 159, wherein in the food or beverage container is manufactured for single service use. 